song-bird n.

"musical or rhythmic vocal utterance," Old English sang "voice, vocal music, song, art of singing; metrical composition adapted for singing, psalm, poem," from Proto-Germanic *songwho- (source also of Old Norse söngr, Norwegian song, Swedish sång, Old Saxon, Danish, Old Frisian, Old High German, German sang, Middle Dutch sanc, Dutch zang, Gothic saggws), from PIE *songwh-o- "singing, song," from *sengwh- "to sing, make an incantation" (see sing (v.)).

Of the musical call of some birds from late Old English. Middle English had songly "worthy of song" (mid-14c.). The colloquial phrase for a song "for a trifle, for little or nothing" is from "All's Well" III.ii.9 (the identical image, por du son, is in Old French). With a song in (one's) heart "feeling joy" is attested by 1930 in Lorenz Hart's lyric. Song and dance as a form of stage act is attested from 1872; the figurative sense of "rigmarole" is by 1895.

"feathered, warm-blooded vertebrate animal of the Aves," Old English bird, a rare collateral form of bridd, originally meaning "young bird, nestling" (the usual Old English for "bird" being fugol, for which see fowl (n.)), which is of uncertain origin with no cognates in any other Germanic language. The suggestion that it is related by umlaut to brood and breed is rejected by OED as "quite inadmissible." The metathesis of -r- and -i- was complete 15c. (compare wright).

Despite its early attestation, bridd is not necessarily the oldest form of bird. It is usually assumed that -ir- from -ri- arose by metathesis, but here, too, the Middle English form may go back to an ancient period. [Liberman]

Up to c. 1400 it still often was used in the specific sense "the young of a bird, fledgling, nestling, chick," and of the young of other animals (bees, fish, snakes) and human children. Compare the usual Balto-Slavic words for "bird" (Lithuanian paukštis, Old Church Slavonic pŭtica, Polish ptak, Russian ptica, etc.), said to be ultimately from the same root as Latin pullus "young of an animal."

The proper designation of the feathered creation is in E. fowl, which in course of time was specially applied to the gallinaceous tribe as the most important kind of bird for domestic use, and it was perhaps this appropriation of the word which led to the adoption of the name of the young animal as the general designation of the race. [Hensleigh Wedgwood, "A Dictionary of English Etymology," 1859]

The figurative sense of "secret source of information" is from 1540s. The colloquial meaning "man, fellow, person" is from 1799.

Bird-watching is attested from 1897. Bird's-eye view "the view as seen from above, as if by a bird in flight," is from 1762. Phrase for the birds in reference to anything undesirable is recorded from 1944, supposedly in allusion to birds eating from droppings of horses and cattle. The bird-spider (1800) of the American tropics is a large sort of tarantula that can capture and kill small birds.

A byrde yn honde ys better than three yn the wode. [c. 1530]

The form with bush is attested by 1630s.