mid-15c., "feed on buds," from Middle French brouster, from Old French broster "to sprout, bud," from brost "young shoot, twig," probably from Proto-Germanic *brust- "bud, shoot," from PIE *bhreus- "to swell, sprout" (see breast, n.). Lost its final -t in English on the mistaken notion that the letter was a past participle inflection. Figurative extension to "peruse" (books) is 1870s, American English. Related: Browsed; browsing.