Does a loanword mean it should be given back at a certain point?

You'll have to ask the Germans who coined the word Lehnwort, and the English person who calqued (loan translation, Lehnübersetzung) it as loanword. It's funny that the other kind of word, Erbwort 'inheritance word', was not calqued. What's even funnier is that German Lehn (Latin feudum, feodum, beneficium) doesn't really mean 'loan', it's 'fief'. A Lehnsmann is a vassal.

Ceci n'est pas un seing.