c. 1400, "to glisten, be dazzling," probably from Old English *glimsian "shine faintly," part of the group of Germanic words in *gl- having to do with "smooth; shining; joyous," from PIE root *ghel- (2) "to shine." If so, the unetymological -p- would be there to ease pronunciation. From mid-15c. as "to glance with the eyes;" from 1779 as "catch a quick view." Related: Glimpsed; glimpsing.