inconvenient (adj.)

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.

late 14c., "fit, suitable, proper; affording accommodation; opportune, favorable," from Latin convenientem (nominative conveniens), present participle of convenire "to come together, meet together, assemble; unite, join, combine; agree with, accord; be suitable or proper (to)," from assimilated form of com "with, together" (see con-) + venire "to come" (from a suffixed form of PIE root *gwa- "to go, come").

Meaning "personally suitable to ease of action or performance" is from late 15c. Sense of "at hand, easily accessible" (1849) is marked in OED as "Ireland and U.S."