I’ve never understood that one, either.
I was Charles growing up. When I went away to college, everyone called me C. R. because it was trendy to use initials way back then. But when I moved back to Houston in 1979, everyone called me Chuck.
Better that than Charlie, I guess.
It’s another rhyming nickname. (Peggy from Meggy from Margaret = Dick from Rick from Richard).
(Daisy as a nickname for Margeret, is because Marguerite is French for Daisy).
That’s what I was going to post.
My sister Peggy is named after our grandmother Peggy. Her legal, birth certificate first name is “Peggy.” For most of her 45 years she’s had to argue with various low-level petty bureacrats who insist “but your real name is Margaret.”
I’m surprised she hasn’t strangled one of them yet.
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It’s derived a term of affection, that probably derived from “chick(en).” It appeared to attach itself as a nickname for “Charles” because the two words had the same first two letters.
Polly is a nickname for Mary. Go figure.
There’s a kind of daisy called Marguerite, and I suppose that’s where it comes from.
Kit for Christopher.
I’m kind of shocked there’s an actual explanation.
Apparently it used to be that the diminutive for a name was -kin, -in, or -cock (heheh). Kind of like the current diminutive is -y. So instead of Johnny like we’d say today, John became Johnkin/Jankin, and from there it got shortened into Jakin and then Jack.
I’m not really a fan of tying Jack to John, anyway. I think it works just fine as a name on its own.
Interesting. Does this survive in any other modern names?
Pumpkin 
Wasn’t Mog one of the names of the little furry guys from Final Fantasy 3???
I’m totally going to name my daughter Mog if it turns out this is a socially acceptable name.
That actually makes sense - marguerite means daisy.
Hmm. I always thought “Jack” was related to “Jacques”, and had no direct descent from “John” in English.
Pepe for Jose.
I’m told that Skip is the nickname for Lesley, but I have no evidence, just the word of one guy called ‘Skip.’ I have also known a Francis called ‘Skip,’ so I’m dubious.
Ted for Edward. What’s wrong with Ed - it’s one letter shorter!
It doesn’t really work for Theodore either. 
Ned is also short for Edward. It doesn’t work for anything.
Hank for Henry is pretty weird.
I know a Sandy - Scottish nickname for Alexander.
Surely a lot of these just come from the fact that so many people used the same names- as well as the custom of naming after previous generations- so you have 3 Edwards in the family, one gets ‘Ed’, one gets ‘Ted’, and the last becomes ‘Ned’ (apparently a contraction of ‘mine Edward’, if you’re wondering). If you read much history- and note it is often very old names that have so many forms- the same names crop up so often, in some eras, people would have to work out some way of telling 'em all apart, and that means lots of versions, even if they don’t make much sense!
Some of those guys had Roman numerals for last names, making it easier to tell them apart.
Mog is a boy! And your daughter can hang out with mine, Relm