noun
immediate deal; deal sealed by a single word
Archaic term for a transaction concluded on the spot with a verbal agreement, without written contract or haggling. Not used in modern business Japanese.
江戸時代の市場では、一口商いで値段が決まることも多かった。
In Edo-period markets, prices were often settled by an immediate verbal deal.
Compound of 一口 (ひとくち, 'one mouthful; a single word') and 商い (あきない, 'trade, business'). The exact historical derivation is uncertain; the term likely reflects the idea of sealing a deal with a single utterance.