"bright flame, fire," Old English blæse "a torch, firebrand; bright glowing flame," from Proto-Germanic *blas- "shining, white" (source also of Old Saxon blas "white, whitish," Middle High German blas "bald," originally "white, shining," Old High German blas-ros "horse with a white spot," Middle Dutch and Dutch bles, German Blesse "white spot," blass "pale, whitish"), from PIE root *bhel- (1) "to shine, flash, burn."
1630s, "light-colored mark or spot" on the face of a horse, cow, etc., northern English dialect, probably from Old Norse blesi "white spot on a horse's face," from Proto-Germanic *blas- "shining, white," from the same root as blaze (n.1). Middle Dutch or Low German cognates of the Norse word also have been suggested as the source. Applied 1660s in American English to marks cut on tree trunks to indicate a track; thus the verb meaning "to mark a trail" (1750). Related: Blazed; blazing.
"to burst into flame, burn brightly or vigorously," c. 1200, from blaze (n.1). To blaze away "fire (guns or cannon) continuously" is by 1776, hence "work with vigor and enthusiasm." Related: Blazed; blazing.
"make public" (often in a bad sense, boastfully), late 14c., of uncertain origin, the verb not being found in Old English; perhaps from Middle Dutch blasen "to blow" (on a trumpet), from Proto-Germanic *blaes-an (source also of German blasen, Gothic -blesan), from PIE root *bhle- "to blow." Or connected to blaze (v.1) on the notion of "shine forth."
"to mark" (a tree, a trail), usually by cutting of a piece of bark so as to leave a white spot, 1750, American English, from blaze (n.) "white mark made on a tree" (1660s), from blaze (n.2).