In the adverbs section later there is the construction "come back" / "tagann ar ais" wich in some sense is synonym with "return".
Apparently you would not use "fillim" to return your books to the library but really rather in the sense of coming back from some place?
That’s what I was going to ask.
This question came up as text only (no speaker icon to tap for sound), and I couldn’t find another link to this word to give me the pronunciation for it. I just assumed it was pronounced the same way I’ve hear Irish folks pronounce “film” before.