lockup

The compound noun 'lockup' is a transparent formation from the native English verb 'lock' and the adverbial particle 'up'. The verb 'lock' originates from the Old English noun loc, referring to a bolt, bar, or fastening, which itself derives from the Proto-Germanic lukan and ultimately the Proto-Indo-European root leug-, meaning 'to bend' or 'to turn', conceptually linked to the action of a key. The particle 'up', from Old English, adds a sense of finality or thoroughness to the action. Thus, the literal sense of 'completely fastened' evolved by the 17th century into the abstract noun denoting both the act itself and, by metonymy, the secure place (like a jail) where someone is completely confined.

Structure: lock (verb) + up (particle) - lock: From Old English loc (a fastening, enclosure), functioning as the core verb meaning to fasten or secure. - up: From Old English up, upp, functioning as an adverbial particle indicating completeness, finality, or intensification.