Word Origin & History
O.E. an, from P.Gmc. *ainaz (cf. O.N. einn, Dan. een, O.Fris. an, Du. een, Ger. ein, Goth. ains), from PIE *oinos (cf. Gk. oinos "ace (on dice)," L. unus "one," O.Pers. aivam, O.C.S. -inu, ino-, Lith. vienas, O.Ir. oin, Breton un "one"). Originally pronounced as it still is in only, and in dial. good
'un, young 'un, etc.; the now-standard pronunciation "wun" began c.14c. in southwest and west England (Tyndale, a Gloucester man, spells it won in his Bible translation), and it began to be general 18c. Use as indefinite pronoun influenced by unrelated Fr. on and L. homo. Slang one-arm bandit "a type of slot machine" is recorded by 1938. One-night stand is 1880 in performance sense; 1963 in sexual sense. One of the boys "ordinary amiable fellow" is from 1893. One-track mind is from 1927.