"nom de guerre" etymology?

I get a word-of-the-day email from wordsmith.org. Recently I got this one:

But “nom de plume” (literally “pen name”) is the more commonly used term for a pseudonym. I always thought “nom de guerre” was a kind of ironic twist on “nom de plume” but never quite got why. And the email above never does explain why nom de guerre would mean pseudonym or how it came into use.

But I know that one of you knows.

I don’t know. However, I just assumed that “nom de plume” referred specifically to authors, while “nom de guerre” referred to any other assumed name (such as performers often use).

“Nom de guerre” was an earlier term – people would enlist in the army under an assumed name, or would take on a more frightening name. The term migrated in French to mean any assumed name and then moved into English.

“Nom de plume” is a back translation of the English “pen name.” The term is not really French (the OED calls it "pseudo-French). It’s a translation of the term “pen name” from English – and is not used in France.

The OED dates “nom de guerre” from 1679 and “nom de plume” from 1823.

Hm, I thought that “nom de guerre” still literally meant a “wartime name”–like “Abu Mazen” (Mahmoud Abbas), or “Che” Guevara, or the pseudonyms adopted by many in the French Resistance (e.g. “Colonel Passy” / Andre Dewavrin).

I hadn’t realized it could mean any assumed name, but the dictionary definitions indicate that it can be any pseudonym used by a person engaged in a certain project–not necessarily a military one.

I dimly recall from my military school days (some thirty-plus years ago), reading in a history text that French soldiers, once upon a time, commonly gave themselves brash or daring nicknames. The only example I recall is Sans Quartier; “without quarter”–that is, “no quarter given” or “no mercy shown”.

At least in books and movies, it used to be common for men to enlist under assumer names in the French Foreign Legion. Michael “Beau” Geste and his brother Digby, IIRC, were known as Smith and Jones.

There was a 15th century Italian mercenary with the intimidating nom de guerre Colleoni (related to Spanish “cojones”), which he chose because he claimed to have three testicles. Before battles, he would call out to the enemy that he was the famous Colleoni with three testicles, and the enemy had better not mess with him.