padlock

The word 'padlock' is a compound formed in Middle English from the elements 'pad' and 'lock'. The origin of 'pad' here is obscure; it may be related to an old word for a path (suggesting a portable lock for use on the road) or, less likely, to 'pad' meaning a toad, perhaps alluding to the shape. The core element, 'lock', derives from the Old English loc, which referred to a fastening, bolt, or barrier, and is of Proto-Germanic origin. The compound thus literally denotes a 'portable lock' or a 'lock with a particular (pad) form', evolving from a descriptive term for a specific physical object into the standard name for this ubiquitous security device.

Structure: pad + lock - pad: (Origin uncertain, possibly from Middle English pad, meaning path or toad; in this compound, its specific sense is obscure, but it functions as a modifier.) - lock: (From Old English loc, meaning a fastening, bolt, or enclosure; functions as the core noun/verb indicating the securing mechanism.)