急ぐ - Wiktionary, the free dictionary

From Old Japanese.^[1] Ultimately from Proto-Japonic *isonku. Appears to be root iso ("earnest? industrious?") + verb-forming suffix -gu of uncertain meaning. Cognate with archaic adjective 勤し (isoshi, “diligent, industrious, hard-working”) and modern verb 勤しむ (isoshimu, “to work diligently, industriously”),^[1] may also be related to adverb いそいそ (isoiso, “cheerfully, unreservedly”), verb 勇む (isamu, “to be in high spirits, to be encouraged”).

First attested as noun form isogi ("hurrying, rushing") in the Man'yōshū of 759.^[1]

• (Tokyo) いそぐ [ìsóꜜgù] (Nakadaka – [2])^[2][3][4]
• IPA^(key): [iso̞ɡɯ̟]

急(いそ)ぐ • (isogu) intransitive godan (stem 急(いそ)ぎ (isogi), past 急(いそ)いだ (isoida))

1. [from late 800s] to hurry, to hasten, to rush, in order to get something done or to get somewhere

   急(いそ)いで片(かた)付(づ)ける

   isoide katazukeru

   to clean up in a rush

急(いそ)ぐ • (isogu) transitive godan (stem 急(いそ)ぎ (isogi), past 急(いそ)いだ (isoida))

1. [from late 900s] to prepare or expedite something

• 遅(おそ)くなる (osoku naru, “slow down”, intransitive)
• 遅(おそ)くする (osoku suru, “slow down”, transitive)
• 遅(おく)らせる (okuraseru, “slow down”, transitive)

• 忙(いそが)しい (isogashii): busy

From Old Japanese.^[1] Further derivation unknown.

First attested in a piece of 催馬楽 (saibara, “court music”) dated to the late 600s, early 700s.^[1]

Homophonic verb 跨ぐ (matagu, “to straddle, to step across”) is likely a derivation of this verb, possibly from the idea of striding, i.e. walking quickly.

• (Tokyo) またぐ [màtáꜜgù] (Nakadaka – [2])^[2]
• IPA^(key): [ma̠ta̠ɡɯ̟]

急(また)ぐ • (matagu) intransitive ^†yodan

1. [roughly 700s–???] (obsolete) to be in a hurry, to be hasty
2. [roughly 700s–???] (obsolete) to be impatient