From The Collaborative International Dictionary of English v.0.48 [gcide]:
Wanderoo \Wan`der*oo"\, n. [Cingalese wanderu a monkey.] (Zool.)
A large monkey (Macacus silenus) native of Malabar. It is
black, or nearly so, but has a long white or gray beard
encircling the face. Called also maha, silenus,
neelbhunder, lion-tailed baboon, and great wanderoo.
[Written also ouanderoo.]
[1913 Webster]
Note: The name is sometimes applied also to other allied
species.
[1913 Webster]