also: すあい
noun
broker; brokerage; brokerage fee
Archaic term for a broker or the fee charged by a broker. Not used in modern Japanese; replaced by words like 仲買人 (なかがいにん) or 手数料 (てすうりょう).
江戸時代の文献には、牙婆が取引の仲介をした記録が残っている。
Records from the Edo period show that 牙婆 acted as intermediaries in transactions.
The exact derivation is uncertain. The kanji 牙 (tusk, fang) and 婆 (old woman) may have been used phonetically or as ateji for the reading すわい/すあい, which likely originated from a native Japanese word for mediation or fee.