mid-14c., from Old French egle, from Old Provençal aigla, from Latin aquila "black eagle," fem. of aquilus, often explained as "dark colored" (bird); see aquiline. The native term was erne. Golf score sense is by 1908 (according to old golf sources, because it "soars higher" than a birdie). The figurative eagle-eyed is attested from c.1600.