broom (n.)

Old English brom, popular name for several types of shrubs common throughout Europe (used medicinally and for fuel) and characterized by long, slender branches and many yellow flowers, from Proto-Germanic *bræmaz "thorny bush" (source also of Dutch braam, German Brombeere "blackberry"), from PIE *bh(e)rem- "to project; a point."

As "twigs of broom tied together to a handle to make a tool for sweeping," mid-14c. Traditionally, both the flowers and sweeping with broom twigs were considered unlucky in May (Suffolk, Sussex, Wiltshire, etc.).