the.com/padlock

means A detachable lock with a shackle that you can hang on a hasp, chain, or gate to secure it, then carry off with you.

from First recorded in the 1400s as a compound of 'pad' plus 'lock' — though 'pad' here is murky. The leading theory ties it to an old dialect word for a pannier basket or hamper, since early padlocks were used to secure baskets and wicker containers; another guess links it to 'paddock' or enclosed yard. Nobody is fully certain, but by the 15th century 'padlok' meant exactly what it means now: a lock you could unclip and take with you, unlike the fixed locks built into doors.