early 15c., "act of assimilating," from Old French assimilacion, from Latin assimilationem (nominative assimilatio) "likeness, similarity," noun of action from past participle stem of assimilare (see assimilate). Psychological sense is from 1855.
assimilation as·sim·i·la·tion (ə-sĭm'ə-lā'shən)
The incorporation of digested substances from food into the tissues of an organism.
The amalgamation and modification of newly perceived information and experiences into the existing cognitive structure.
The process by which a person or persons acquire the social and psychological characteristics of a group: “Waves of immigrants have been assimilated into the American culture.”