quisling

Named after Vidkun Quisling, the Norwegian officer who led the Nazi collaborationist government in occupied Norway during World War Two; the term entered use in 1940, while the war was still unfolding. His surname itself was a Latinized coinage, Quislinus, based on the Danish place name Kvislemark.

The surname looked like it meant 'one from Kvislemark,' using a suffix for personal origin, but it was really built from Latin -inus attached to Kvisle(mark). Only later did people reinterpret that ending as the Norwegian suffix -ing, denoting a person of a certain kind — which is exactly the sense that let 'quisling' generalize from a single traitor's name into a word for any collaborator.

Kvislemark comes from Danish kvissel, 'cleft branch,' itself from Old Norse kvísl, 'fork in a road,' tracing back to Proto-Germanic *twīsilō — the same root behind English twistle, twissel, and twizzle, all words about splitting or forking.