An adjective glossed “large, extensive, wide” (PE17/42), “roomy, wide, extensive” (PE17/42), or “vast, huge” (PE17/99) that Tolkien used to explain the suffix -ion seen in names like Eregion and Nanduhirion. It was derived from primitive ✶yānā based on the root √YAN, where the ancient long ā became au. It seems this adjective was sometimes used as a suffix meaning “✱wideness, region”, and as a suffix the au reduced to o as was generally the case in polysyllables.
Conceptual Development: Tolkien had some variations of this adjective in a few places in his writings. In one place he had iand derived from √YAN or √YAD “wide” as an explanation for suffix -iand also seen in land names (PE17/115). In another he explained -ion as a blend of √YŎNO “wide, extensive” and √YOD “fence, enclose” (PE17/43), where presumably the adjective Sindarin for “wide” was ✱iond as a cognate of Q. yonda “wide, roomy, extensive” (PE17/43).
adj. large, extensive, wide, vast, huge. Q. yāna-. >> -ion