also latchkey, "a key to raise or draw back the latch of a door" and allow one to enter from outside, 1825, from latch (n.) + key (n.1). Latchkey child first recorded 1944, American English, in reference to children coming home from school while both parents are away at work.
Many elementary school principals and teachers have always known the "latchkey" child or the "eight-hour orphan." [New York State Teachers Association, "New York State Education," 1944]
The older or simpler device was a latch-string, which could be pulled in to lock up; having it out was symbolic of openness.
past tense and past participle of catch (v.), attested from 14c., predominant after c. 1800, replacing earlier catched. A rare instance of an English strong verb with a French origin. This might have been by influence of Middle English lacchen (see latch (v.)), which also then meant "to catch" and was more or less a synonym of catch (as their noun forms remain), and which then had past tense forms lahte, lauhte, laught. The influence would have happened before latch switched to its modern weak conjugation.
1845, among some American native peoples, "a gift," from Chinook jargon pot-latch, "a gift," from Nootka (Wakashan) patshatl "giving, gift." Later (1865) in sense "An Indian feast, often lasting several days, given to the tribe by a member who aspires to the position of chief, and whose reputation is estimated by the number and value of the gifts distributed at the feast" [Century Dictionary, 1895]