envenom

Etymology

From Middle English envenymen, from Old French envenimer (“to poison, taint”); equivalent to en- + venom.

verb

1. (transitive) To inject or put venom onto or into (someone or something).
   Ah dearest, whoso sucks a poisoned wound Envenoms his own veins! 1833, Robert Browning, Pauline
   The Kayans of Central Borneo ascribe souls to the trees which yield the poison they use to envenom their arrows. 1890, James George Frazer, The Golden Bough, volume 2, page 17
2. To acerbate, make bitter.