1620s, "place in the hands of another as a pledge for a contract," from Latin depositus, past participle of deponere "lay aside, put down, deposit," also used of births and bets, from de "away" (see de-) + ponere "to put, place" (past participle positus; see position (n.)). From 1650s as "lay away for safe-keeping;" from 1749 as "lay down, place, put." Related: Deposited; depositing.
1620s, "state of being placed in safe-keeping," from Latin depositum, from deponere (see deposit (v.)). From 1660s as "that which is laid or thrown down." Geological sense is from 1781; financial sense "money lodged in a bank for safety or convenience" is from 1737. Middle English had depost "thing entrusted for safe-keeping" (late 14c.).