Etymology
Advertisement
latch (v.)
Old English læccan "to grasp or seize, catch hold of," also "comprehend," from Proto-Germanic *lakkijanan. Not found in other Germanic languages; according to Watkins probably from PIE *(s)lagw- "to seize" (see lemma). In its original sense the verb was paralleled and then replaced by French import catch (v.). Meaning "to fasten with a latch" is mid-15c. Related: Latched; latching.
Related entries & more 
Advertisement
latch (n.)
"device for catching and retaining," especially "a fastening for a door," late 13c., probably from latch (v.).
Related entries & more 
unlatch (v.)
1640s, from un- (2) "reverse, opposite of" + latch (v.).
Related entries & more 
latch-key (n.)

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.

Related entries & more 
letch (n.)
"craving, longing, strong desire," 1796 [Grose], perhaps a back-formation from lecher, or deformed from a figurative use of latch (v.) in a secondary sense of "grasp, grasp on to." Or perhaps from letch (v.), a variant of leach.
Related entries & more 
Advertisement
caught 

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.

Related entries & more 
latchet (n.)
"strap or thong of a sandal or shoe," late 14c., lachet, from Old French lachet, variant of lacet, diminutive of las, laz "noose, string, cord, tie" (see lace (n.)). Spelling altered perhaps by influence of latch.
Related entries & more 
locket (n.)
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.
Related entries & more 
haggaday (n.)
mid-14c., "a kind of door latch," and said to be still the name for rings for raising thumb-latches in the north of England. It appears to be what it looks like: what you say when you open the door ("have good day," as in the 1414 record of them as hafgooddays).
Related entries & more 
potlatch (n.)

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]

Related entries & more