late 15c., "blown over, passed away" (as a wind or storm), past-participle adjective from verb overblow "to blow over the top of," of a storm, "to abate, pass on" (late 14c.), from over- + blow (v.1). Sense of "past the time of blossoming or blooming" (as a flower), 1610s, is from blow (v.2). Figurative meaning "inflated, puffed up" (with vanity, etc.) is from 1864.