ᴱQ. súyon appeared in the Qenya Lexicon of the 1910s with the glosses “nephew, daughter’s son”, a combination of ᴱQ. sui “daughter” and ᴱQ. yon “son” (QL/87). It also appeared in the Poetic and Mythological Words of Eldarissa with the gloss “nephew” (PME/87). Based on its cognate G. fwion “nephew, properly sister’s children”, I think it is more likely this word means “sister’s son” rather than “daughter’s son”.

Neo-Quenya: I would retain this word in Neo-Quenya as a now-obscure elaboration of √YON “son”, but since there are no other words for “nephew” in Quenya, I would use it for male children of any sibling.