indecision 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.

mid-15c., "act of deciding," from Old French décision (14c.), from Latin decisionem (nominative decisio) "a decision, settlement, agreement," noun of action from past-participle stem of decidere "to decide, determine," literally "to cut off," from de "off" (see de-) + caedere "to cut" (from PIE root *kae-id- "to strike").

Meaning "final judgment or opinion in a case" is from 1550s. Meaning "quality of being decided in character, ability to make prompt determinations" is from 1781; sense of "a resolution, a fixing of purpose" is by 1886.  Decision-making (adjective) is recorded by 1946.