1915, in telegraphs, where punctuation had to be spelled out and quote and unquote were used in place of the quotation marks; from un- (2) "reverse, opposite of" + quote (v.). Quote unquote together to indicate quotation of the word or phrase to follow (often with ironic intent) is from 1942.
unquantifiable
unquenchable
unquestionable
unquestioned
unquiet
unquote
unravel
unreachable
unread
unreadable
unready