jefesse:
One time I started compiling a personal spanking thesaurus, like what you've described. I should track it down and post it somewhere.
I had also done that. Here is what I came up with. There are a lot of synonyms, though I doubt the list is exhaustive. Exhausting, perhaps, but likely not exhaustive. Pardon the spelling on some of them.
Hiney
Rear
Rear end
Hindquarters
Derriere
Seat
Backside
Behind
Tuchus
Bottom
Cheeks
Cakes
Pound cakes
Ass
Posterior
Part that jumped over the fence last
Tail
Booty
Cooley
Buttocks
Butt
Buns
Hot cross buns
(tan your) hide
Asscheeks
Caboose
Bum
Moon
Fanny
Rump
Glutes
Gluteus maximus
Globes
Nether region
Tush
Kiester
Can
Azz
Breech
Fundament
Haunches
Duff