it's actually beau, from the French (came to America from French settlers in the deep south, hence its popularity among black culture), its meaning was originally partner (as in "here comes Madonna and her latest beau"), but is usually spent & pronounced 'boo' in rap culture.
oh rightio- gotcha now....couldn't work out where you were coming from with that one Mrs C. Glad you explained, at my age a wrinkled forehead from concentrating is so not wise!