late 14c., "action of putting a person outside the protection of the law by legal means," from Anglo-French utlagerie, a hybrid from Old English utlaga (see outlaw (n.)) + -ary. Meaning "defiance of the law" is by 1869.
Old English utlaga "one put outside the law" (and thereby deprived of its benefits and protections), from a Scandinavian source such as Old Norse utlagi (n.) "outlaw," from utlagr (adj.) "outlawed, banished," from ut "out" (see out (adv.)) + *lagu, plural of lag "law" (see law). Formerly it was lawful for anyone to kill such a person.
[G]if he man to deaðe gefylle, beo he þonne utlah ["Laws of Edward & Guthrum," c.924]
Meaning "disorderly person living in defiant violation of the law, one living a lawless life" is recorded by 1880. As an adjective, from Old English.
adjective and noun word-forming element, in most cases from Latin -arius, -aria, -arium "connected with, pertaining to; the man engaged in," from PIE relational adjective suffix *-yo- "of or belonging to." The neuter of the adjectives in Latin also were often used as nouns (solarium "sundial," vivarium, honorarium, etc.). It appears in words borrowed from Latin in Middle English. In later borrowings from Latin to French, it became -aire and passed into Middle English as -arie, subsequently -ary.
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Definitions of outlawry from WordNet
illegality as a consequence of unlawful acts; defiance of the law;