1650s, "occurring without external stimulus," from Late Latin spontaneus "willing, of one's free will," from Latin (sua) sponte "of one's own accord, willingly," a word of uncertain origin. Related: Spontaneously; spontaneousness. Used earlier of persons and characters, with a sense "acting of one's own accord" (c. 1200). Spontaneous combustion first attested 1795. Spontaneous generation (the phrase, not the feat) attested from 1650s.
)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}