Word that means "outdated name"

These terms are holdovers from a previous era.

You could say that it's an anachronism.

Such expressions are perhaps edging towards fossilised metaphor.

Archaism is defined as: An archaic word, phrase, idiom, or other expression.

And archaic itself has a linguistics-related definition (see #3 below)

archaic [ɑːˈkeɪɪk] adj 1. belonging to or characteristic of a much earlier period; ancient 2. out of date; antiquated an archaic prison system 3. (Linguistics) (of idiom, vocabulary, etc.) characteristic of an earlier period of a language and not in ordinary use