An adjective appearing as G. guin “own, held, possessed” in the Gnomish Lexicon of the 1910s, above another entry G. guig “a piece of property”, with a brace indicating the two entries had been combined (GL/43). It was likely based on gui the past form of G. gôtha- “possess, have, hold” (GL/42).

Neo-Sindarin: For purposes of Neo-Sindarin, I would update this adjective to ᴺS. garnen “owned, held, possessed” as the passive participle of N. gar- “hold, have” from The Etymologies of the 1930s derived from the root ᴹ√GAR (Ety/GAR). Compare N. garn “property” from the same root.