Merriam-Webster's Collegiate® Dictionary, 11th Edition
VOW
I. noun
Etymology: Middle English vowe, from Anglo-French vou, from Latin votum, from neuter of votus, past participle of vovēre to vow; akin to Greek euchesthai to pray, vow, Sanskrit vāghat sacrificer
Date: 13th century
a solemn promise or assertion,
II. verb
Date: 14th century
transitive verb to promise solemnly ; swear , to bind or consecrate by a vow, intransitive verb to make a vow, vower noun
III. transitive verb
Etymology: Middle English, short for avowen
Date: 14th century
avow , declare