I get the need to have a distinction between fish flesh and other meats such as beef, pork, and chicken, but using the same logic as in this article, I've always thought of fish as part of the general "meat" category. It confuses me how Catholics do the "no meat, yes fish" thing. Maybe there's some etymological explanation for why our current-day definition of meat doesn't explicitly have this distinction (assuming it ever did), but if there is, that context seems to have been lost long ago. For some reason, many people now just reflexively believe that fish is not meat -- even non-Catholics.

It has to do with old abstinence laws which stated that meat comes from “land animals” and classified fish as a separate category of creature.

And Kosher laws are absolute insane. Fish must have scales but can't be bottom feeders. Land animals have to have specific types of hooves. Can't mix types of fabric...and other silly stuff that might have had a basis in logic at some point but has been lost.

Yeah, as I understand, these were attempts at guidelines for avoiding diseases, because e.g. pork goes bad very quickly.

But we didn’t properly figure out how diseases spread until well past the Middle Ages, so that’s why they seem to so random…

It also didn’t help that in ancient times pigs apparently had a propensity for digging up graves and eating corpses… (Not 100% sure if this is true, but my high school teacher was Jewish and mentioned that as one of the main reasons for why pork isn’t kosher)