They mean something only to you, your parents, and your siblings, and maybe a cousin or two.
On my way home last night, I grabbed a fish sandwich from the drivethru and started thinking about “fried idunno with woofit sauce”. Before I was born, when my bro and sis were wee bairns, Mom was making fried flounder filets for dinner. The sibs came home from school and asked “what’s for dinner?” Mom replied “Oh, I don’ know” My sis, the older of the two asked “and how are you preparing the ‘idunno’?” “Fried” My bro asked “What’s the sauce wif’ it?” So from then on, ever time we had fried fish with tartart sauce, it was Fried Idunno with Woofit sauce.
Thinking about that got me thinking ab out another family word: Years ago, some cousins were visiting for dinner while I was away at college. In the course of conversation they started discussing childhood memories, and got around to favorite candies. They could all remember a particular one - the flavor, texture, packaging, cost, everything but the name. It drove them batty trying to remember it. It got late and cousins left to go home. Much later, at around 3am, the phone rings. Dad picks it up quickly (because the only calls in the middle of the night are either bad news or a wrong number) and hears the cousin say “Joe? Walnettos!” and hang up. To this day, “walnettos” is anything we can remember clearly but cannot recall its name.
I meant to add:
What are your Family Words
“toon” (Who Framed Roger Rabbit?) is shorthand for “Mom is acting crazy again, but it’s not dangerous”. My bros discovered Mom was a toon when I threatened with never again talking to any of my relatives unless they all went to see the movie ASAP, including Dad, who hadn’t been to the movies in 12 years.
“need a d2” means “anybody got a coin” (what, I introduced my bros to table RPGs)
“who’s driving?” for “who has the TV’s remote?” “Dude, I have the wheel but who took the engine” means “ok, I have the TV’s remote… now where the heck is the cable box’s remote?”
From playing the Star Wars table RPG. A friend, whose character was a Jedi, would say “I feel a botijo in the Force” whenever his “premonition” or similar rolls went badly (a botijo is a specific kind of earthenware pot, they cool water). So when someone is shooting out of his ass, we say he’s feeling a botijo in the Force.
My father had numerous words he used in place of actual swear words, they were usually some variation on the word “fart”. The most notorious was “fart-blossom”. I ended up making him a bouquet of fart-blossoms once. They were little butt-shaped flowers with little bubbles coming out of them, made from Sculpey. There was also dingle-fartz and dingleberry but we eventually learned that dingleberry was an actual slang word.
Eventually dad gave up all pretense of not swearing in front of us and went to the real swear words. I never knew dad was a sailor.
We have “mmmmmfriends” in my family.
This is used to denote anyone whose relationship to anyone else you’re not quite certain on the status of, or anyone whose relationship to anyone else is even marginally likely to cause raise eyebrows in the most conservative or any relationship that isn’t quite kosher or you just don’t want to go into.
Gay lovers? mmmmmmmmmmfriends.
Straight lovers who may or may not be still together? mmmmmmmmmmfriends.
Bookie/drug dealer/stripper from bachelor party waving to you in the mall? mmmmmmmfriends.
One of the other sides of a dramatic love triangle you’re involved in? mmmmmmmmfriends.
In the case of the members of my family in medical, legal or law enforcement professions meeting a client/suspect/snitch outside of work? mmmmmmmfriends.
So useful!
In my family, we have “ominot” (umbrella) and “obagadees” (ice cream), which were my sister’s mispronunciations when she was young.
My wife and I have “bacony”: if you are hogging the bed, you are being bacony, and you need to move over. It started out as a quote from the old Sizzleens commercial (“Move over, bacon!”).
When Mr. Lissar was little, he used to refuse to eat anything with cricks or criggens in them, those being mysterious, unidentified things that he doesn’t like. For instances, “I don’t wanna eat that soup. It’s got cricks innit”.
The term surfaces at family dinners, when his father will ask him gravely if there are any cricks in anything before serving.
In my family, one of my sisters coined the word “green guppers” when trying to pronounce “cucumber” and that’s what they’ve been called ever since.
Fudda Hudda.
When the kids were younger we often played the fire hydrant game to pass the time while in the car. The winner was the person who “claimed” the most fire hydrants along the way. To “claim” a hydrant you must yell “Fire Hydrant!” and point it out to the other palyers. Once my daughter, in her haste to claim a hydrant, yelled something that sounded like “Fudda Hudda!”. It stuck.
We use the term “cognomen syndrome” to descrbe someone whose name matches something about them, such as Dr. Foote the podiatrist.
My parents call each other Mr and Mrs P after the Piggles in Pogo.
I think Pop is too uptight to use made-up words. 
When my brother was little his name for helicopter was ninga-ninga, for the sound it made. And my sister who could not pronounce any of our names but was apparently overly fond of the “D” consonant named us “Dee,” “Dar-dar,” and “Dumm.” We still call each other that sometimes.
My husband and I have a couple words we’ve made up in conversations to each other. “Goojaba” means “I miss you.” and sometimes we say Lalaba, ijahba, ohdaba, which are all interchangeable and have no real meaning but my best approximation is something like “Hi. I love you.”
Rice Krispie Marshmallow Treats are called “marshmallow poopies” in our house. I learned it from an old girl friend (pre-dating my wife, and for the life of me can’t remember why she called them that), and have passed it on to my children. (Nothing else from that prior relationship is ever referenced…just marshmallow poopies.)
“Mee-mo” is money in my family. That was how I said “money” when I was a baby, and it stuck.
My grandmother always used to exclaim, “God Free Moses!” (kind of like saying “goodness gracious!”), and until I was probably in high school, I always heard it as “Godfrey Moses!”- I always wondered who that guy was…
Dad said that when working on carpentry jobs with his pa that he was told to use as few words as possible to save time. So common phrases were over-shortened.
“Mer” meant “pass me the hammer, please”
So “mer” meant hammer.
It also meant “camera”. When in a park if someone spotted a deer or something he would say “mer” and whoever was closest to the camera would pass it over to him.
Heh, we’ve got a few.
From my son’s little kid mispronunciations, we get girl cheese for grilled cheese, heckadopter and hairplane and hairport for helicopter, airplane and airport.
My husband, and avowed atheist, some years back made it a point to leave god out of his swearing. So now we get “by the nostrils!” and simply “nostrils!”. The explanation is somewhat complicated, and my husband and I are role players (the table top kind, perverts!) and so it goes a bit like this.
Gzortch is the 13 nostriled god of snot (er…yeah, there’s a story that goes with how he is, don’t ask.). So anything where you would normally say god, you’d use notrils, not wishing to take Gzortch’s name in vain, lest you sneeze for evermore. Thus, the above occurs, frequently.
Fnergin, Furbblehead and other words like this are simply random prounoucements, sometimes accompanying an unsual event, or in the absence of an appropriate swear. “Fnergin! I left my keys RIGHT HERE! By the nostrils! I’m sick of this, who moved my keys?!”
My husband is a bit strange. I love him, but he’s a bit strange.
“Penis!” is another random pronouncement, one that means “That is a very random thing you just said.” In more polite company, an abrupt change of subject is introduced with “speaking of polar bears”. (there is a story behind the penis! one, which I thought I told here but cannot now find, so hopefully someone with better search fu can or I can give the quick and dirty, if you’re interested.)
We also use various World of Warcraft terms. (yeah, yeah, its Geek House.) So QQ (cry more - meaning stop whining, basically), zerg, nerf, ninja, and noob are thrown around in casual conversation, as is FTW and FTL. “Spaghetti FTW (for the win).” means “That spaghetti was really good!”
Yeah, its weird here. 
Cheers,
G
My fiancee’s family have passed on a few words to me. They use “chunch” to mean cuddling or sleeping or otherwise being comfortable. We are often chunching or just chunchy together.
Their baby words for pee and poop are tata and gronks. The dogs know these terms, and like to go “out tata gronks.”
My favorite is my cousin’s term for grandpa. She had trouble with it when she was a baby so grandpa was “Bumpa.”
Actually, it sounds fun there. I think I might commandere “by the nostrils!”
This actually sounds like it could actually be a medieval, religious oath: “By the nostricls of Our Saviour!!” Like how “God’s wounds!” became “zounds”.
We call difficult and random tasks that my mother wants completed ‘Ummagunnas’. So if she wants brother to cover the basement entirely in hand-ornamented tile, I would tell him “Mom has an ummmagunna for you.” My mom also uses it to get us to stop complaining about work. So if she asks me to take out the trash she will say “Please take out the garbage and don’t get that look in your face, its not an ummagunna.”