"long-necked, long-legged wading bird," c. 1300, from Old French hairon, eron (12c.), earlier hairo (11c., Modern French héron), from Frankish *haigiro or some other Germanic source, from Proto-Germanic *hraigran. Related to Old High German heigaro, Danish hejre "heron," German Reiher, Dutch reiger, Old Norse hegri), perhaps from a common IE root imitative of its cry (compare Old Church Slavonic kriku "cry, scream," Lithuanian krykšti "to shriek," Welsh cregyra "heron," Latin graculus "jackdaw, crow"). Old English cognate hraga did not survive into Middle English. Egret is from the same source.
fem. personal name, originally another form of Jane, Janey and a diminutive of Jane or Janet; in modern use (mid-20c.) typically a shortening of Jennifer. Jenny is attested from c. 1600 as female equivalent of jack (n.), and like it applied to animals (especially of birds, of a heron, a jay, but especially Jenny wren, 1640s, in bird-fables the consort of Robin Redbreast). Also like jack used of machinery; Akrwright's spinning jenny (1783) is said to have been named for his wife, but is perhaps rather a corruption of gin (n.2) "engine."
large grallatorial bird with very long legs, beak, and neck, Old English cran, common Germanic (cognates: Old Saxon krano, Old High German krano, German Kranich, and, with unexplained change of consonant, Old Norse trani, Danish trane), from PIE *gere-no-, suffixed form of root *gere- (2) "to cry hoarsely," also the name of the crane (cognates: Greek geranos, Latin grus, Welsh garan, Lithuanian garnys "heron, stork"). Thus the name is perhaps an echo of its cry in ancient ears.
Misapplied to herons and storks. The gray European crane was "formerly abundant in marshy places in Great Britain, and prized as food" [OED], but was extinct there though much of 20c.
Use for "machine with a long arm for moving weights" is attested from late 13c. (a sense also in equivalent words in German, French, and Greek). The constellation was one of the 11 added to Ptolemy's list in the 1610s by Flemish cartographer Petrus Plancius after Europeans began to explore the Southern Hemisphere.