glacial adj.

Proto-Indo-European root meaning "cold; to freeze." 

It forms all or part of: chill; cold; congeal; cool; gel; gelatine; gelatinous; gelato; gelid; glace; glacial; glaciate; glaciation; glacier; glaciology; glacis; jell; jelly.

It is the hypothetical source of/evidence for its existence is provided by: Latin gelare "to freeze," gelu "frost," glacies "ice;" Old English cald "cold, cool," German kalt.

mid-15c., of weapons, "strike obliquely without giving full impact," a nasalized form of glacen "to graze, strike a glancing blow" (c. 1300), from Old French glacier "to slip, make slippery" (compare Old French glaciere "part of a knight's armor meant to deflect blows"), from glace "ice" (see glacial). Sense of "look quickly" (first recorded 1580s) probably was by influence of Middle English glenten "look askance" (see glint (v.)), which also could account for the -n-. Related: Glanced; glancing.