insuperable 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.

Proto-Indo-European root meaning "over."

It forms all or part of: hyper-; insuperable; over; over-; sirloin; somersault; soprano; soubrette; sovereign; sum; summit; super-; superable; superb; superior; supernal; supra-; supreme; sur-.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit upari, Avestan upairi "over, above, beyond;" Greek hyper, Latin super "above, over;" Old English ofer "over," German über, Gothic ufaro "over, across;" Gaulish ver-, Old Irish for.

"surmountable," 1620s, from Latin superabilis "that may be overcome," from superare "to overcome, surmount, go over, rise above," from super "over" (from PIE root *uper "over") + -abilis (see -able). The negative formation insuperable is older and more common and superable may be a back-formation from it.