1826, noun of action from acclimate.
1792, from French acclimater, verb formed from à "to" (see ad-) + climat (see climate). Related: Acclimated; acclimating. The extended form acclimatize is now more common.
acclimation ac·cli·ma·tion (āk'lə-mā'shən)n.
The process of becoming adjusted to a new environment or situation.