spar (n.1)
early 14c., "rafter;" late 14c., "stout pole," from or cognate with Middle Low German or Middle Dutch sparre, from Proto-Germanic *sparron (cognates: Old English *spere "spear, lance," Old Norse sperra "rafter, beam," German Sparren "spar, rafter"), from PIE root *sper- (1) "spear, pole" (see spear (n.1)). Nautical use, in reference to one used as a mast, yard, boom, etc., dates from 1630s. Also borrowed in Old French as esparre, which might be the direct source of the English word.
spar (v)
late 14c., "go quickly, rush, dart, spring;" c.1400, "to strike or thrust," perhaps from Middle French esparer "to kick" (Modern French éparer), from Italian sparare "to fling," from Latin ex- (see ex-) + parare "make ready, prepare," hence "ward off, parry" (see pare). Etymologists consider a connection with spur unlikely. Used in 17c. in reference to preliminary actions in a cock fight; figurative sense of "to dispute, bandy with words" is from 1690s. Extension to humans, in a literal sense, with meaning "to engage in or practice boxing" is attested from 1755. Related: Sparred; sparring.
spar (n.2)
"crystalline mineral that breaks easily into fragments with smooth surfaces," 1580s, from Low German Spar, from Middle Low German *spar, *sper, cognate with Old English spær- in spærstan "gypsum."