Etymology: Middle English, from Old English ānlīc, from ān one — more at one
Date: before 12th century
1. unquestionably the best ; peerless
a. alone in a class or category ; sole <the only one left> <the only known species> b. having no brother or sister <an only child> 3. few <one of the only areas not yet explored> II. adverb Date: 14th century 1. a. as a single fact or instance and nothing more or different ; merely <has only lost one election — George Orwell> b. solely, exclusively <known only to him> 2. at the very least <it was only too true> 3. a. in the final outcome <will only make you sick> b. with nevertheless the final result <won the battles, only to lose the war> 4. a. as recently as ; not before <only last week> <only in the last year did she get recognition> b. in the immediate past <only just talked to her> Usage: The placement of only in a sentence has been a source of studious commentary since the 18th century, most of it intended to prove by force of argument that prevailing standard usage is wrong. After 200 years of preachment the following observations may be made: the position of only in standard spoken English is not fixed, since ambiguity is avoided through sentence stress; in casual prose that keeps close to the rhythms of speech only is often placed where it would be in speech; and in edited and more formal prose only tends to be placed immediately before the word or words it modifies. III. conjunction Date: 14th century 1. a. with the restriction that ; but <you may go, only come back early> b. and yet ; however <they look very nice, only we can't use them> 2. were it not that ; except <I'd introduce you to her, only you'd win her — Jack London>
New Collegiate Dictionary. 2001.