Known locally as Mkunkhu but also known as Monkey Thorn.
From the Useful Tropical Plants Database
Senegalia galpinii is a deciduous tree with a spreading crown that can grow from 8 – 30 metres or more tall. The bole, which is usually straight and branches from quite high up, is up to 60cm in diameter, occasionally to 150cm. The branchlets are glabrous to shortly hairy, with pairs of hooked, blackish prickles up to 1 cm long just below the nodes.