1592: A Fish That Was Never a Fish: crayfish

Crayfish are not true fish, but their name is not so totally misnomered as it might first appear. 'Crayfish', and the later variant 'crawfish' come from the French 'crevice', originally from a Germanic word related to the modern word 'crab', having the natural relation to another crustacean. It was only later on that the latter syllable of 'crevice' had altered and became understood as 'fish' by association.

Check out the new Word Theory about why the word 'religion' might be so tricky to nail down.