indeterminism (n.)

word-forming element meaning "not, opposite of, without" (also im-, il-, ir- by assimilation of -n- with following consonant, a tendency which began in later Latin), from Latin in- "not," cognate with Greek an-, Old English un-, all from PIE root *ne- "not."

In Old French and Middle English often en-, but most of these forms have not survived in Modern English, and the few that do (enemy, for instance) no longer are felt as negative. The rule of thumb in English has been to use in- with obviously Latin elements, un- with native or nativized ones.

1846, introduced by William Hamilton for "doctrine of the necessitarian philosophers" (who hold that human action is not free but necessarily determined by motives, regarded as external forces acting on the will or character of the person). See determine + -ism.

Determinism does not imply materialism, atheism, or a denial of moral responsibility; while it is in direct opposition to fatalism and to the doctrine of the freedom of the will. [Century Dictionary]

 From 1876 in general sense of "doctrine that everything happens is determined by a necessary chain of causation," from French déterminisme, from German Determinismus, perhaps a back-formation from Praedeterminismus.