@mafketis
Quite. Nouns for nationalities don't sound great in English, with a few historical exceptions, mainly close to England or with historical contact, like Poles, Finns, Spaniards, Arabs, Scots. Turks, Swedes, Danes. Many others are either derogatory and/or military slang, Chinaman, Kraut, Frog, Wop, Dago, Mick, Seppo, Kellper, Yanito, Saint, Saffer, or slurs about black, gypsy and Pakistani people.
Poles which sounds discriminatory.
As you know, English is one of the least gendered Indo-European languages, and given that pole can mean kij or laską, putting an -ess doesn't sound comfortable.
Anyway, try it with Finn and people will think you're talking about bridge.