Meaning

noun thin curly wood shavings used for packing or stuffing

originFrom Latin excelsior, comparative of excelsus (“high”). The name of the stuffing material was originally a trademark. As an exclamation, originating in Henry Wadsworth Longfellow's poem Excelsior (1841), based on the New York state motto. Popularized in the comic book fandom by Marvel Comics editor Stan Lee, who chose the term to sign off his columns as it was an obscure term and would confound…

Etymology from Wiktionary, CC BY-SA 3.0