The name contains the common Finnic suffix -inen. While it may have been folk-etymologically associated with ääni(“sound”), it is probably from a Sami substrate[1] (going back to a common hydronymic element *ään-, *eän-(“large”), akin to Proto-Samic [Term?], compare Äänekoski). The name probably first referred to the lake ("large lake") and only later to the river (Äänisjoki). Related to KarelianIänisjärvi, LivviIänizjärvi and VepsÄnine.