The Collaborative International Dictionary of English v.0.48:
Baboo \Ba"boo\, Babu \Ba"bu\ (b[aum]"b[=oo]), n. [Hind. b[=a]b[=u].] A Hindu gentleman; a native clerk who writes English; also, a Hindu title equivalent to the English Mr. or Esquire. --Whitworth. [1913 Webster]WordNet (r) 3.0 (2006):
baboo n 1: used as a Hindi courtesy title; equivalent to English `Mr' [syn: babu, baboo]