The OED:
Forms:
ME–16 bragman, 15 bramane, 16–18 brachman(e, brachmin, 16 brackman, braman, bramen, bramine, braminy, 17–18 bramin, 17– brahmin, 18 brahman.
Etymology:
< Sanskrit brāhmana, < brahman praise, worship; some of the older English forms were derived from or influenced by the Greek spelling βραχμᾶνες (plural), Latin brachmāni, brachmānes, and medieval Latin corruptions; the form Brahmin,
a corruption of the Indian vernacular pronunciation, is still all but
universal in popular use; during the 19th cent. Orientalists adopted the
more correct Brahman, which (often written Brâhman or Bráhman) is employed by most writers on India.