1530s, from extreme + -ly (2). Originally "with great severity," later more loosely, "in extreme degree" (1570s).
extremely interesting
extremely unpleasant
extremely cold
extravaganza
extravasation
extraversion
extraverted
extreme
extremely
extremeness
extremism
extremist
extremities
extremity
)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}