c.1200, from Old English blostm, blostma "blossom, flower, fruit," from Proto-Germanic *blo-s- (cf. Middle Low German blosom, Dutch bloesem, German Blust), from PIE *bhlow-, extended form of *bhel- (3) "to thrive, bloom," possibly identical with *bhel- (2) "to blow, inflate, swell" (see bole). This is the native word, now largely superseded by bloom and flower.