I received this from wire telegraph historian, Gregor Ulsamer, DL1BFE.

Gregor Ulsamer, DL1BFE said:

When I remember right, CQ was an abbreviation of "communiquer" or
"communiqué" in telegraph language.

73

GU

That sounds much more likely because Paris was the home of the International Telegraphers Union (ITU).

73
DR
N1EA