yo

conj. “and”, “often used between two items of any part of speech that were by nature or custom clearly associated, like the names of spouses Manwë yo Varda, or “sword and sheath” *macil yo vainë, “bow and arrows” *quinga yo pilindi, or groups like “Elves and Men” Eldar yo Fírimor – but contrast eldain a fírimoin dative forms in FS, where Tolkien joins the words with a, seemingly simply a variant of the common conjunction ar. – In one source, yo is apparently a preposition "with" yo hildinyar = *"with my heirs", SD:56.