depth

The word 'depth' is a native English formation. It derives from the Old English adjective 'dēop', meaning deep, which itself has Proto-Germanic origins ('deupaz') and a probable Proto-Indo-European root 'dʰewb-', signifying deep, hollow, or dim. The addition of the nominal suffix '-th' (from Old English '-þu') transformed the adjective into an abstract noun, a common Germanic process seen in pairs like 'wide/width' and 'long/length'. Thus, 'depth' literally means "the state or quality of being deep," a concrete measurement that later extended metaphorically to describe intensity, emotion, and intellectual profundity.

Structure: dep (deep) + th (noun suffix) 'dep' is a variant of the root 'deep', originating from Old English 'dēop' (deep, profound). 'th' is a noun-forming suffix from Old English '-þ(u)', '-þo', '-þ', used to create abstract nouns from adjectives.