First clear attestation dates to the 19th cent. A 15th cent. recording of ñonio is of unclear meaning. From Late Latin nonnus "monk," "elderly person."
Reconstructed by de Vaan (2014) as from Proto-Indo-European *nVnV "daddy," "nanny."
Dialect Variants: Cuba ñongo "indiscrete," Venezuela ñongo "insecure," "high-maintenance" (nonicus). Note zero palatalization in Costa Rica, Honduras, Nicaragua noneco "silly," which reflects Vulgar Latin *nonus with suffix -eco, indicating deformity. Also note 12th cent. variant nana "married woman."
Romance: Western Vulgar Latin: Italian nonno ; Eastern Vulgar Latin: Romanian nun
Celtic: Brythonic: Welsh nain "grandmother"
Balto-Slavic: East Slavic: Russian njánja "child nanny" South Slavic: Bulgarian neni "elder"
Albanian: nënë "mother"
Hellenic: Ancient Greek νάννας (nánnas) "uncle," "aunt"
Indo-Iranian: Indo-Aryan: Sanskrit nanā́ "mother"Double palatalization of Latin n-nn- > Spanish ñ-ñ- is unusual, though not unheard of, and may have been deformed by children's speech. This may reinforce the theory that various *nVn- words in Vulgar Latin are of nursery origin (cf. niño, nene, nona).