mid-15c., "otherwise called," from Latin alias "at another time, in another way," from alius "(an)other," from PIE *al- (1) "beyond" (cognates: Sanskrit anya "other, different," Avestan anya-, Armenian ail, Greek allos "another," Gothic aljis "other," Old English elles "otherwise, else," Modern English else).

"assumed name," c.1600, from alias, adv..