c. 1600, from event + -ful. According to OED, it is in Shakespeare, once ("As You Like It"), and there is no record of it between then and Johnson's "Dictionary." Related: Eventfully; eventfulness. Eventless is attested from 1815.
the most exhausting and eventful day of my life
an eventful decision
evening
evenly
evenness
evensong
event
eventful
eventide
eventual
eventuality
eventually
eventuate
)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}