Is it ensure, insure, or assure?
c.1400, "to glisten, be dazzling," probably from Old English *glimsian "shine faintly," from Proto-Germanic *glim- (see gleam). If so, the intrusive -p- would be there to ease pronunciation. Sense of "catch a quick view" first recorded mid-15c. Related: Glimpsed. The noun is recorded from mid-16c.; earlier in verbal noun glimpsing (mid-14c.).