Blazer
late 19th century: from blaze1 + -er1. The original general sense was ‘a thing that blazes or shines’ (mid 17th century), giving rise to the term for a brightly coloured sporting jacket.
wiktionary
From blaze + -er. Originates from the 'blazing' scarlet jackets worn by members of Lady Margaret Boat Club, the rowing club associated with St. John's College, Cambridge. Compare Old English blæsere, blasere(“burner, incendiary”, literally “blazer”).
etymonline
blazer (n.)
1630s, "anything which blazes;" 1880 as "bright-colored loose jacket," in this sense British university slang, from blaze (n.1), in reference to the red flannel jackets worn by the Lady Margaret, St. John College, Cambridge, boating club. Earlier the word had been used in American English in the sense "something which attracts attention" (1845).
