What's the "een" in Halloween?
c.1300, from Old French espoillier "to strip, plunder," from Latin spoliare "to strip of clothing, rob," from spolium "armor stripped from an enemy, booty;" originally "skin stripped from a killed animal," from PIE *spol-yo-, perhaps from root *spel- "to split, to break off" (cf. 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 "to damage so as to render useless" is from 1560s; that of "to over-indulge" (a child, etc.) is from 1640s (implied in spoiled). Intransitive sense of "to go bad" is from 1690s. To be spoiling for (a fight, etc.) is from 1865, from notion that one will "spoil" if he doesn't get it. Spoil-sport attested from 1801.
"goods captured in time of war," c.1300; see spoil (v.). Spoils system in U.S. politics attested by 1839, commonly associated with the administration of President Andrew Jackson, on the notion of "to the victor belongs the spoils."
To kill; waste: You wanted to hate his guts so it would be easier to spoil him? (1980s+)