押金
yā jīn · HSK 5
deposit
💰 押金 = 押 (pledge) + 金 (money/gold) — money pledged as security
押 means to pawn or pledge something; 金 is gold or money. Together: money handed over as a pledge, returned when conditions are met. Common for rentals and rentals deposits.
押 — hand radical 扌 + 甲 (jiǎ, phonetic)
押 is a semantic-phonetic compound. The hand radical 扌 supplies the meaning of pressing or holding down with the hand, while 甲 gives the sound. From the literal sense of pressing, it extended to signing/sealing documents, mortgaging, and detaining — all involving an authoritative 'pressing' action.
金 — roof 亼 + two dots (metal nuggets) + earth 土
Originally a pictograph of metal nuggets buried in the earth beneath a covering, with the two dots representing pieces of ore. It first meant 'metal' broadly, then narrowed to 'gold' as the most precious metal, and by extension 'money'.