n.
  - a rope or strap placed around the head of an animal and used to lead or tether it. ▸archaic a noose for hanging a person. 
- a strap passing behind the neck by which the bodice of a sleeveless dress or top is held in place.
v.
  - put a halter on (an animal).
- archaic hang (someone).
Etymology
  OE hælftre, of Gmc origin, meaning ‘something to hold things by’; rel. to helve.