Ping did reach me, though I'm not sure what I can contribute. German has its share of these words too, of course, I think they're called Modalpartikel. The most notorious is probably ja.
Doch is another one that one could probably fill pages trying to explain...
Interestingly, Georges uses these modal words frequently in his Latin-German dictionary, e.g. quoniam is translated as "weil denn, weil nun, da ja, da doch, da einmal".
@cmw Not sure there is a comprehensive work, but then I'm not familiar with the literature...
@cmw Often, when there are "why" questions on this site (e.g. "Why is the perfect passive not amavitur?"), I'm tempted to say "Because the Romans talked like that," and it would be a perfectly correct answer. But people want to hear about Proto-Indo-European etc. 😔
