1. to thrive, flourish, prosper , Lat. florere, vigere, (Herdotus Historicus):—;with dative to abound in a thing, (Homeric Hymns)

2. Pass. in same sense, οἱ Λακεδαιμόνιοι εὐθηνήθησαν (Herdotus Historicus); τὴν πόλιν εὐθενεῖσθαι (Demosthenes Orator)

derivation uncertain (ML)