The headword is found mainly (from Homer onwards) as an epithet of Zeus. This entry hedges its bets between the two possible etymologies of it (see LSJ s.v.); modern scholarship has not eliminated either but tends to the first.
[1] In Homer and elsewhere the present headword itself, eu)ru/opa, is sometimes used as a nominative (and vocative); for an instance see under alpha 2371 = tau 1133; but it is also used as an accusative (as indeed is implicit in the glosses here), theoretically implying the nominative given (only) here.