Middle English word locket comes from Proto-Indo-European *leug, and later Proto-Germanic *luką (An opening; aperture; hole. Lock. Shutter.)

Detailed word origin of locket

Dictionary entry	Language	Definition
*leug	Proto-Indo-European (ine-pro)
*luką	Proto-Germanic (gem-pro)	An opening; aperture; hole. Lock. Shutter.
loc	Old English (ang)	Lock.
lok	Old Norse (non)
loc	Middle English (enm)
loc	Anglo-Norman (xno)
locket	Middle English (enm)

Words with the same origin as locket