Origin and history of incessant

"unintermitted continuance," 1610s, from incessant + abstract noun suffix -cy.

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.

Proto-Indo-European root meaning "to go, yield."

It might form all or part of: abscess; accede; access; ancestor; antecede; antecedent; cease; cede; cession; concede; decease; exceed; excess; incessant; intercede; necessary; precede; predecessor; proceed; recede; recess; recession; secede; secession; succeed; success.

It might also be the source of: Sanskrit sedhati "to drive, chase away;" Avestan apa-had- "turn aside, step aside;" Latin cedere "to yield, give place; to give up some right or property," originally "to go from, proceed, leave;" Old Church Slavonic chodu "a walking, going," choditi "to go."