means A mechanical or digital device that secures something shut and opens only with the right key, combination, or credential — or, as a verb, the act of fastening it that way.

from From Old English 'loc,' meaning an enclosure, bolt, or bar — anything that fastens. It traces back to a Proto-Germanic root (compare Old Norse 'lok,' a lid or cover, and German 'Loch,' a hole) carrying the idea of closing up or shutting fast. The same word also gave us 'lock' as in a lock of hair — possibly from a related sense of something that holds or interlinks together — though the two meanings have drifted far apart over the centuries.