Late 19th century; earliest use found in Allan Pinkerton (1819–1884), private detective. From out [preposition, interjection] + -en<br>Old English (in an earlier sense). Cognate with Old Frisian ūta, Old Saxon ūtan, ūtana, Old High German ūzan, ūzana, Old Icelandic útan, Swedish uten, Danish uden, Gothic ūtana (translating ancient Greek ἔξωθεν from outside) from the Germanic base of out [preposition, interjection] + a Germanic adverbial suffix; for a parallel formation with different suffixation compare out [preposition, interjection].