I might have jumped the gun a bit here.
Underwear writing did not used to be defined, so I created a wiki entry for it and populated it with Calvin Klein posts.
However, during gardening (which I was slightly too zealous with) I realised that its prior use was for "text on panties" posts.
For now, I've changed some of these posts to clothes_writing print_panties but I'm open to revert & create a new tag for CK-style underwear.