Sort of? Part of the reason I caught it was that the name was mentioned in the previous book.
Back in book 1, there was a mention of Iax being some important ‘lost in the mists of the past’ legendary type figure. Iax the Namer.
When K and Co. are searching for the bandits, the girl merc tells the story of “Jax and the Moon” where the f-ed up little kid takes off with the tinker’s pouch and hunts down the moon because he loves her, and imprisons her name in a half-assed house (that he put together badly because he didn’t know how), and now because he has her name trapped there, she has to come visit regularly.
Later in book 2, K listens while Felurian tells about how the moon moves back and forth between faen and the human world, and how Namers created the faen realm out of whole cloth because they wanted to, and how Iax loved the moon and wanted her to be with him.
Even later, Iax comes up again (I think Bast talks about him) in a side note about how powerful and screwed up Namers and magic people were back in the misty long ago.
Each of those instances are TOTALLY thrown out there as sidenotes, not given any undue importance, just kindof tossed out in the middle of all the other random stuff that happens. It’s just a nice sort of … hey, that’s that dude the story was about, and hey, wonder what the past WAS like to have people creating something like faen and then forgetting that it existed… whoa, some dude really did steal part of the moon…
Nothing earthshatteringly important or spoilery or even foreshadowing really, just a nice touch to have in there.