I found this article interesting, and thought it might make a good contribution to this thread:
That was quite good. #7, “fro” caught my attention. Apparently there was a usage of “froward” that fell out of favor, probably because it is to easy to mistake for “forward”, but has been partially replaced by “untoward”, a word that puzzled me (in terms of origins) for the longest time.
IMO, the 1920s Jazz Age introduced the most colorful slang into the English language, much of which stood the test of time. There’s a pretty good sampling on this site.
These two definitions seem ever so slightly off to me.
This PDF site appears more accurate and expanded.
Some Dr. Hepcat…
Thank you, @solost , for that link. I always wondered what “running roughshod over” meant.
I henceforth resolve to work “carve your knob” into a conversation every day.
Reminds me of widget, once the name of a Gilette product of which I have a couple.
link:
A turd floater
(It’s raining cats and dogs…I just stepped in a poodle)
The “Valley Girl” speak—tubular, gnarly, grotty to the max, gag me with a spoon—was mercifully short-lived.
But not the ending every sentence like it was a question? That’s stuck around?
My mother was shocked at the use of bitchin’ as an adjective (eg. Have a bitchin’ summer!) in my yearbook back in the mid to late 60s. It was surfer slang then.
Totally tubular, dude! 
Heh … now that I hear it in my head imaging circa 60s surfers, I could see absolutely see “bitchin’” at home there.
I wonder if the relatively recent phenomenon of vocal fry is an evolution of ‘Valley Girl speak’…?
…and the adoption of the word ‘like’ as a quotative…
toad choker
whence
(Not slang or idiom, means from which place or source, so don’t put “from” in front of it!)
Yes, this page seems a good cite. I’d heard the Cockney rhyming slang derivation before; that’s the one I’m rooting for.