1670s (figurative); 1760s (literal), from un- (1) "not" + past participle of alloy (v.).
unalloyed metal
unalloyed pleasure
unadvertised
unaffected
unafraid
unaided
unalienable
unalloyed
unalterable
unaltered
unambiguous
un-American
unanimity
)window.location='https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=byronic106@yahoo.com&lc=US&item_name=Donation+to +Help+Keep+Etymonline+Free+and+Open&no_note=0&cn=&curency_code=USD&bn=PP-DonationsBF:btn_donateCC_LG.gif:NonHosted'){kind=link}