Like others I'd an ancestor "Cissie" - we thought she'd been a "Cecilia" or a "Celia" - but eventually we discoverd she was an "Elizabeth Ann" - oldest sister to a long troupe of younger siblings, - who all faithfully called her "Cissie" on all communications!
I'd asked on RootsChat before if anyone knew why the Christian name "Doris" was popular in the early 20th C - I'd found a few. No one seemed to find a really good reason/ person to fit to have started the craze....
"Fanny" in my lot all started out as "Frances" ( from time to time spelled in the male way as "Francis") which sounds quite posh - but they weren't.
Names we never seem to meet now: Brenda, Doreen, Glenda, Mildred....
In class registers we used to comment on the new intake's names - and the spellings! De-Bra, Diyyann, etc. Once there was a Sean (Shaun) who thought his name was pronounced "Sea - Ann", as he didn't answer to the name called by his teacher, on the register!
Flower names, and "double names ( Daisy-Jane, Lily-Ann, Mary-Rose) seem to be more popular again for girls