勇む

From Old Japanese. Initial いさ (isa) portion shares its origin with the old isa reading of 鯨 (“whale”). Ending む (mu) is likely the old auxiliary verb む, expressing intent, desire, or estimation.

Homophonic with archaic 営む (“to do business”), and archaic 諫む/諌む (“to admonish”), but semantic relationship is unclear.

勇(いさ)む • (isamu) intransitive godan (stem 勇(いさ)み (isami), past 勇(いさ)んだ (isanda))

1. to be in high spirits, enthusiastic; to be brave or courageous
2. (archaic) to whinny
   • This sense is usually expressed using the word 嘶く (inanaku). However, the ending naku portion is homophonic with 泣く (“to cry, to weep”), and as such this word was treated as somewhat taboo by soldiers, who thus used isamu instead.
3. (archaic) to blow a horn as a signal in a naval battle

勇(いさ)む • (isamu) transitive godan (stem 勇(いさ)み (isami), past 勇(いさ)んだ (isanda))

1. (archaic) to encourage, to cheer someone up

• (encourage): 勇(いさ)める (isameru)
• (whinny): 嘶(いなな)く (inanaku)