assuetude

noun2

1. •
   The condition of an organism that has acquired tolerance of a drug or poison.

   • The boy had been his companion for years: and from assuetude had become, as it were, a part of himself. — 1836
2. •
   (no longer used) Accustomedness; habit.

   • Assuetude of things hurtful doth make them lose their force to hurt. — 1627