emptor--prophetes.ai

‖ emptor Rom. Law.
  (ˈɛmptɔː(r), -ə(r))
  [a. L. emptor, agent-n. f. emĕre to buy.]
  A purchaser.

1875 Poste Gaius i. (ed. 2) 108 He had to utter the formula..i.e. to invite the emptor to strike the scale with the ingot.

Oxford English Dictionary