"a box with a lock" (for keeping valuables, etc.), 1855, from lock (n.1) + box (n.1). Earlier as the name of the metal box containing the external lock mechanism on a door.

mid-14c., "iron cross-bar of a window," from Old French loquet "door-handle, bolt, latch, fastening" (14c.), diminutive of loc "lock, latch," from Frankish or some other Germanic source (compare Old Norse lok "fastening, lock;" see lock (n.1)). Meaning "little ornamental case with hinged cover" (containing a lock of hair, miniature portrait, etc.) first recorded 1670s. Italian lucchetto also is from Germanic.

"a maker of locks," early 13c., from lock (n.1) + smith (n.).

1802, in military writing, to describe a very tight style of mass marching, from lock (n.1) + step (n.).

Lock-step. A mode of marching by a body of men going one after another as closely as possible, in which the leg of each moves at the same time with and closely follows the corresponding leg of the person directly before him. [Thomas Wilhelm, "Military Dictionary and Gazetteer," Philadelphia, 1881]

Figurative use by 1836.

earliest form of the musket-lock, fired by means of a match in the form of a cord (called a match-cord), 1690s, from match (n.1), in reference to the firing mechanism, + lock (n.1) in the firearm sense (1540s). They were superseded by flint-locks toward the end of 17c.

"hole or indentation in the gunwale of a boat where an oar rests," mid-14c., or-lok, from oar + lock (n.1).

"removable lock with a pivoted bow or hasp," late 15c., pad-lok, from lock (n.1), but the first element is of obscure origin; perhaps originally, as some sources suggest, "a lock for a pannier."

1550s, "person who picks locks;" 1590s, "instrument for picking and opening a lock;" from pick (v.) + lock (n.1).

Old English wedlac "pledge-giving, marriage vow," from wed + -lac, noun suffix meaning "actions or proceedings, practice," attested in about a dozen Old English compounds (feohtlac "warfare"), but this is the only surviving example. Suffix altered by folk etymology through association with lock (n.1). Meaning "condition of being married" is recorded from early 13c.