From Latin 'affluere' (to flow toward) — wealth 'flows toward' the affluent, like a river receiving tributaries.
Definition
Having a great deal of money; wealthy; (in geography) a tributary stream that flows into a larger river.
The Full Story
Latin15th centurywell-attested
From Latin affluentem (present participle of affluere, to flowtoward, to abound), from ad- (toward) + fluere (to flow), from PIE *bhleu- (to swell, to overflow). The original sense was strictly hydraulic: a tributary stream flowing toward a larger river was an affluent, a usage retained in geography today. The wealth sense arose because Roman rhetoricimagined
back to the same Indo-European image of water in motion. Key roots: ad- (Latin: "toward"), fluere (Latin: "to flow"), *bhleu- (Proto-Indo-European: "to swell, to overflow, to flow").