yardyoudaoicibaDictgodict[yard 词源字典]
yard: Yard ‘enclosed area’ [OE] and yard ‘three feet’ [OE] are distinct words, both of ancient ancestry. The former probably goes back ultimately to Indo-European *ghorto-, which also produced Latin cohors ‘court’ (source of English cohort and court) and hortus ‘garden’ (source of English horticulture) and Russian gorod ‘town’ (as in Leningrad).

Its prehistoric Germanic descendant was *gard-, which, as well as providing English with yard, has produced garden, garth [14] (via Old Norse), and the second syllable of orchard. Yard ‘three feet’ originally meant ‘stick, rod’ (a sense preserved nautically, as in yardarm [16]). It goes back ultimately to prehistoric Germanic *gazdaz ‘pointed stick’ (source of the gad of gadfly [16], etymologically the fly with the ‘sting’).

From this was derived West Germanic *gazdjō, which evolved into German gerte ‘sapling, riding cane’, Dutch gard ‘twig, rod’, and English yard. The Anglo-Saxons used the term as a unit of measurement of land, equal to about five metres (what later became known as a rod, pole, or perch), but its modern use for ‘three feet’ did not emerge until the 14th century.

=> cohort, court, garden, garth, horticulture, orchard; gadfly[yard etymology, yard origin, 英语词源]
yard (n.1)youdaoicibaDictgodict
"patch of ground around a house," Old English geard "fenced enclosure, garden, court; residence, house," from Proto-Germanic *gardaz (cognates: Old Norse garðr "enclosure, garden, yard;" Old Frisian garda, Dutch gaard, Old High German garto, German Garten "garden;" Gothic gards "house," garda "stall"), from PIE *ghor-to-, suffixed form of root *gher- (1) "to grasp, enclose," with derivatives meaning "enclosure" (cognates: Old English gyrdan "to gird," Sanskrit ghra- "house," Albanian garth "hedge," Latin hortus "garden," Phrygian -gordum "town," Greek khortos "pasture," Old Irish gort "field," Breton garz "enclosure, garden," and second element in Latin cohors "enclosure, yard, company of soldiers, multitude").

Lithuanian gardas "pen, enclosure," Old Church Slavonic gradu "town, city," and Russian gorod, -grad "town, city" belong to this group, but linguists dispute whether they are independent developments or borrowings from Germanic. As "college campus enclosed by the main buildings," 1630s. In railway usage, "ground adjacent to a train station or terminus, used for switching or coupling trains," 1827. Yard sale is attested by 1976.
yard (n.2)youdaoicibaDictgodict
measure of length, Old English gerd (Mercian), gierd (West Saxon) "rod, staff, stick; measure of length," from West Germanic *gazdijo, from Proto-Germanic *gazdjo- "stick, rod" (cognates: Old Saxon gerda, Old Frisian ierde, Dutch gard "rod;" Old High German garta, German gerte "switch, twig," Old Norse gaddr "spike, sting, nail"), from PIE root *ghazdh-o- "rod, staff, pole" (cognates: Latin hasta "shaft, staff"). The nautical yard-arm retains the original sense of "stick."

Originally in Anglo-Saxon times a land measure of roughly 5 meters (a length later called rod, pole, or perch). Modern measure of "three feet" is attested from late 14c. (earlier rough equivalent was the ell of 45 inches, and the verge). In Middle English and after, the word also was a euphemism for "penis" (as in "Love's Labour's Lost," V.ii.676). Slang meaning "one hundred dollars" first attested 1926, American English. Middle English yerd (Old English gierd) also was "yard-land, yard of land," a varying measure but often about 30 acres or a quarter of a hide.