Redden comes from red + -en (verb-forming suffix). Red is from Old English rēad, from Proto-Germanic *raudaz, from Proto-Indo-European *h₁rewdʰ- ('red'). The historical chain includes Old English rēad, Proto-Germanic *raudaz, and Proto-Indo-European *h₁rewdʰ-. Older glosses in the chain include "red", which help explain the semantic range of the modern word. Morphologically, redden is best read as compound, suffixal formation, and borrowing, yielding an English verb shaped by both form history and later usage. In current English it functions as a verb, with the sense "to make or become red, especially to flush or blush". English derivatives include reddened and reddening; related forms include red, reddish, and ruddy. The result is an English verb whose etymology preserves the older forms while supporting the word's specialized modern meaning.