What's the "een" in Halloween?
c.1300, from Anglo-French and Old French vou, from Latin votum "a vow, wish, promise, dedication," noun use of neuter of votus, past participle of vovere "to promise solemnly, pledge, dedicate, vow," from PIE root *ewegwh- "to speak solemnly, vow" (cf. Sanskrit vaghat- "one who offers a sacrifice;" Greek eukhe "vow, wish," eukhomai "I pray").
c.1300, from Old French vouer, from vou (see vow (n.)). Related: Vowed; vowing.
sacred voluntary promise to dedicate oneself or members of one's family or community to a special obligation that goes beyond usual social or religious requirements.