1970 as colloquial shortening for improvisation. The famous New York City comedy club, founded in 1963, was, in full, The Improvisation.
imprompt
impromptitude
impromptu
improper
impropriety
improv
improvable
improve
improvement
improvidence
improvident
)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}