halter vs string up

halter is a noun but string up is not a noun.

Word	Noun	Adjective	Verb	Adverb
halter	Yes	No	Yes	No
string up	No	No	Yes	No

As verbs, string up is a hypernym of halter; that is, string up is a word with a broader meaning than halter:

Other hypernyms of halter include hang.

halter (noun)	string up (noun)
either of the rudimentary hind wings of dipterous insects; used for maintaining equilibrium during flight
a woman's top that fastens behind the back and neck leaving the back and arms uncovered
rope or canvas headgear for a horse, with a rope for leading
a rope that is used by a hangman to execute persons who have been condemned to death by hanging

halter (verb)	string up (verb)
prevent the progress or free movement of	add as if on a string
hang with a halter	kill by hanging