This word appeared as G. gôf “fruit (esp. of tree)” in the Gnomish Lexicon of the 1910s (GL/38, 40), the equivalent of ᴱQ. yáva under the early root ᴱ√ẎAVA (QL/105). In Gnomish of the 1920s, long ā became ō rather than further developing into au as it did in later Noldorin and Sindarin. Indeed, this word had become N. iau in The Etymologies of the 1930s, but there it was glossed “corn” (Ety/YAB). The element iof “fruit” did appear in some later words such as N. iofog “fruit drink” (TMME/53), but there the au had become o as it usually did in polysyllables, which the prevented the final f [v] from being lost.

Neo-Sindarin: Ryszard Derdzinski proposed the neologism ᴺS. iaf “fruit” in Parf Pith ’Wain (PPW) from the early 2000s, extracted from iavas “autumn”. It is likely derived from a primitive form *yăbǝ with short ă preventing it from becoming au and absorbing the final f [v]. Based on this, my preferred Sindarin neologism for “fruit” is ᴺS. iâf, though I think the â should be long as is usually the case in monosyllables.