brood: [OE] Like breed, brood came from a prehistoric Germanic base *brōd-, whose ultimate source was Indo-European *bhrē- ‘burn, heat’ (its other English descendants include braise, breath, and probably brawn). The underlying notion of brood is thus not so much ‘reproduction’ as ‘incubation, the warmth that promotes hatching’. The verbal sense ‘worry’ developed in the 18th century. => braise, brawn, breath, breed