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"a turning away from," 1590s; figurative sense of "mental attitude of repugnance" is from 1650s, from Middle French aversion and directly from Latin aversionem (nominative aversio), noun of action from past participle stem of aversus "turned away, backwards, behind, hostile," itself past participle of avertere (see avert). Earlier in the literal sense of "a turning away from" (1590s). Aversion therapy in psychology is from 1950.
aversion a·ver·sion (ə-vûr'zhən, -shən)
A fixed, intense dislike; repugnance, as of crowds.
A feeling of extreme repugnance accompanied by avoidance or rejection.