Stories We Like: A Guide to the Comma
c.1300, compound of all + ready (adj.); literally "fully ready." Cf. Norwegian, Danish allerede "already." Colloquial use in U.S. as a terminal emphatic (e.g. enough, already!) is attested from 1903, translating Yiddish shoyn, which is used in same sense. The pattern also is attested in Pennsylvania German and in South African.