The word for “potato” in the Gnomish Lexicon of the 1910s was G. grothorf (with a deleted alternate form {grothor >>} grothrof), a combination of G. groth “earth” and G. orf “apple”, similar to French “pomme de terre” (GL/42). This same document had another form G. podod for “potato” (GL/64), perhaps a phonetic adaptation of the European word.

Neo-Sindarin: For purposes of Neo-Sindarin, I would adapt this word as ᴺS. cevorf “potato, (lit.) earth-apple” using the later element ᴹ√KEM for “earth”.