From OE læccan (to seize, catch), via PGmc *lakkijaną. The noun named the agent of the verb — the latch is 'the catcher'. The verbal sense survives intact in 'latch onto'. Germanic domestic vocabulary (door, lock, bolt, latch) outlasted the Norman Conquest because the house was the last place French reached.
A fastening device for a door or gate, consisting of a bar that drops into a notch or slot — from Old English læccan (to seize, catch), the latch being literally 'the catcher'.
The word 'latch' traces back to Old English 'læccan', a strong verb meaning 'to seize, catch, grasp, or take hold of'. This verb was in common use throughout the Anglo-Saxon period. The transition from verb to noun is semantically transparent: the latch is literally 'the catcher' — the mechanical device that catches and holds a door shut. This nominalization from a verbal root is a well-attested pattern in Old English word-formation. The Old English noun form, attested as 'læcce' or 'lache', denoted a snare or trap — again, something that catches and holds. This sense
The verb came before the noun. Old English læccan meant to seize or catch — vigorous, physical action. The latch on the door was named as 'the catcher', the mechanism that seizes and holds. This naming logic compressed the verb into an object, but the original energy never fully disappeared: 'latch onto' — to grab hold of an idea or a person — is the same Old English verb, unchanged in sense, walking back into the language after a thousand years underground.