Old English spillan "destroy, mutilate, kill," also in late Old English "to waste," variant of spildan "destroy," from Proto-Germanic *spilthjan (cognates: Old High German spildan "to spill," Old Saxon spildian "destroy, kill," Old Norse spilla "to destroy," Danish spilde "lose, spill, waste," Middle Dutch spillen "to waste, spend"), from PIE *spel- (1) "to split, break off" (cognates: Middle Dutch spalden, Old High German spaltan "to split;" Greek aspalon "skin, hide," spolas "flayed skin;" Lithuanian spaliai "shives of flax;" Old Church Slavonic rasplatiti "to cleave, split;" Middle Low German spalden, Old High German spaltan "to split;" Sanskrit sphatayati "splits").Sense of "let (liquid) fall or run out" developed mid-14c. from use of the word in reference to shedding blood (early 14c.). Intransitive sense "to run out and become wasted" is from 1650s. Spill the beans recorded by 1910 in a sense of "spoil the situation;" 1919 as "reveal a secret." To cry for spilt milk (usually with negative) is attested from 1738. Related: Spilled; spilt; spilling.

1845, originally "a throw or fall from a horse," from spill, v.. Meaning "the spilling of a liquid, amount of spilled stuff" is from 1848.