Green’s Dictionary of Slang

batty n.1

also batta
[Anglo-Ind. batta, an extra allowance given to troops or public servants while serving in the field or on a variety of special postings; also subsistence money given to prisoners, witnesses etc. The payment to soldiers, orig. restricted to field service, became recognized as a regular perk of Indian service, irrespective of the posting; the word comes from Hind. bhata, ult. f. bhat, an advance without interest made to a ploughman or bat, a pack-saddle (as used in the field)]

wages, tips.

Show quotations
[UK]T.E. Hook ‘Merton’ Sayings and Doings 1st Ser. II 323: Wondering whether he should get a command [...] whether he could draw full batta in peace-time.
G.R. Gleig Thomas Munro I 271: He would rather live on half-pay in a garrison that could boast of a fives-court, than vegetate on full batta where there was none.
, , [UK]Hotten Sl. Dict.
[UK]Sl. Dict.
[Ind]Yule & Burnell Hobson-Jobson (1994) 72: batta, s. [...] an extra allowance made to officers, soldiers, or other public servants, when in the field, or on other special grounds; also subsistence money to witnesses, prisoners, and the like.
[UK]Brewer Dict. of Phrase and Fable 103/1: Batta or Batty (Hindustanee). Perquisites; wages. Properly, an allowance to East Indian troops in the field.