1540s, "make compensation for, spend, pay for" (a sense now archaic); 1570s, "satisfy by payment," from Old French defraier, defrayer (15c.), perhaps from de- "out" (see de-) + fraier "spend," from frais "costs, damages caused by breakage," from Latin fractum, neuter past participle of frangere "to break" (from PIE root *bhreg- "to break").
Proto-Indo-European root meaning "to break."
It forms all or part of: anfractuous; Brabant; bracken; brake (n.1) "stopping device for a wheel;" brake (n.2) "kind of fern;" brash; breach; break; breccia; breeches; brioche; chamfer; defray; diffraction; fractal; fraction; fractious; fracture; fragile; fragility; fragment; frail; frangible; infraction; infringe; irrefragable; irrefrangible; naufragous; ossifrage; refract; refraction; refrain (n.); refrangible; sassafras; saxifrage; suffragan; suffrage.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit (giri)-bhraj "breaking-forth (out of the mountains);" Latin frangere "to break (something) in pieces, shatter, fracture;" Lithuanian braškėti "crash, crack;" Old Irish braigim "break wind;" Gothic brikan, Old English brecan "to break."