(covers information from several alternate timelines)
A locker was a storage compartment sealed with a door that could be locked. Lockers were generally used to store hand equipment, weapons, or personal items. Lockers were small enough that an average human could not step into one, and were therefore distinct from storage rooms. A lockers' interior could be subdivided by shelves for more efficient storage.
Lockers used for storing personal belongings and uniforms were installed in residential hallways of California class starships in 2380. The decentralization of the lockers and their proximity to crew berths allowed easy access for crew members. (LD: "Second Contact")