Late 19th century; earliest use found in George Bernard Shaw (1856–1950), playwright and polemicist. Irregularly from prestige + -ous, after vertiginous, magnitudinous, multitudinous, etc.
Definition of prestiginous in US English:
prestiginous
adjective
rare
Viewed in terms of prestige; prestigious.
Origin
Late 19th century; earliest use found in George Bernard Shaw (1856–1950), playwright and polemicist. Irregularly from prestige + -ous, after vertiginous, magnitudinous, multitudinous, etc.