pubis and pubis_bulge have been tagged a handful of times:
https://e621.net/posts?tags=pubis
https://e621.net/posts?tags=pubis_bulge

Usage ranges from the pubic_boot of dinosaurs to a large public_mound. Since both tags see usage and aren't technically the same, and bulge has a different definition than the pubic_boot, I'm not sure whether to alias these together, disambiguate, and/or move both to invalid individually. What do you think would be the best course of action here? I'm leaning toward moving them to invalid since they're so open-ended that a disambiguation would be pretty broad and direct to many different potentially intended tags.

IMO disambiguation is best. I don't think there are so many things that the disambig could point to that the disambig would be useless (the tag tag_(disambiguation) has so many things I had to collect and keep track of all of when going through it myself a while back, so this wouldn't be the first)

I also think disambiguation might be good because people trying to tag the pubic_boot of a dinosaur character might not be totally familiar with that term, but know the pubis bone instead.