fatten

The verb 'fatten' is a transparent English formation built upon the native adjective 'fat'. The core concept of 'fat' as an adjective denoting plumpness or well-fed condition can be traced back to Proto-Germanic faitida-, likely from a Proto-Indo-European root meaning 'to blow, swell'. The addition of the productive Old English suffix '-en' (as seen in 'widen', 'sharpen') directly creates the causative verb meaning 'to make fat'. This logical compounding illustrates a classic pattern in English word formation, where a descriptive quality is transformed into an action that induces that quality, originally applied to livestock and later extended metaphorically to finances or quantities.

Structure: fat (adjective) + en (verb-forming suffix) "Fat" originates from Old English fǣtt, meaning 'fatted, plump', with Proto-Germanic roots. In this word, it functions as the core adjective describing a state of plumpness or excess flesh. "En" is a verb-forming suffix from Old English -nian, used to create verbs meaning 'to make or become' from adjectives or nouns.