Glimpse originally meant 'a faint flash of light', not 'a brief look'. It belongs to the gl- family of English light words — gleam, glimmer, glint, glitter — all from a Proto-Germanic root meaning 'to shine'.
A momentary or partial view of something; a brief, incomplete look.
From Middle English glimsen meaning 'to glimmer, to shine faintly', from a Germanic base related to Old English glæm meaning 'gleam, brightness' and Middle High German glimsen meaning 'to glow'. The original sense was not about seeing but about shining — a glimpse was a faint flash of light. The shift from 'a brief shine' to 'a brief look' happened by the 15th century: if light appears only for a moment, you only see it briefly. The entire glim- family
English has an unusual cluster of gl- words that all relate to light: gleam, glimmer, glint, glitter, glow, gloss, glare, and glimpse. Linguists call this a phonaestheme — a sound cluster that carries meaning without being a formal morpheme. The gl- pattern for light words appears across Germanic languages and may trace back thousands of years