the.com/nom de plume

means A pen name — a fictitious name a writer uses instead of their real one, usually on the cover.

from French-looking, but actually an English invention: literally 'name of pen,' coined in the 1800s by English speakers imitating the real French borrowing 'nom de guerre' (war name, an alias soldiers took up). The French themselves don't use 'nom de plume' — they say 'nom de plume' only when borrowing it back from English, bemused. So the phrase is a kind of linguistic costume itself: dressed in French grammar, built by English hands.