(linguistics) a specific historical consonantal shift of the Japanese language during the Heian Period, wherein many word-medial /f/ sounds changed to /w/ sounds

Japanese angelica tree (Aralia elata)

squeeze out / force out a whisper / rack one's brains

Alternative spelling of 働き詞: (archaic, grammar) any word that declines or conjugates; (archaic, grammar) more specifically, a verb