also yardarm, 1550s, from yard (n.2) in the nautical sense (attested from Old English) + arm (n.1). In 19c. British naval custom, it was permissible to begin drinking when the sun was over the yard-arm.
Entries linking to yard-arm
yard n.2
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" (source also of 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" (source also of 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.
arm n.1
[upper limb of the human body], Middle English arm, from Old English earm, from Proto-Germanic *armaz (source also of Old Saxon, Danish, Swedish, Middle Dutch, German arm, Old Norse armr, Old Frisian erm), from PIE root *ar- "to fit together" (source also of Sanskrit irmah "arm," Greek arthron "a joint," Latin armus "shoulder").
Arm of the sea was in Old English. Arm-twister "powerful persuader" is from 1915. Arm-wrestling is from 1899.
They wenten arme in arme yfere Into the gardyn [Chaucer]