c. 1300, from joint (adj.) + -ly (2). It seems to have chased out joinly (early 15c.).
this paper was written jointly
join
joinder
joiner
joint
jointed
jointly
jointure
joist
joke
joker
jokester
)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}