curb
Pronunciation: /kəːb/
noun
- 2 (also curb bit) a type of bit with a strap or chain attached which passes under a horse’s lower jaw, used as a check.
- 3North Americanvariant spelling of kerb
verb

Origin:
late 15th century (denoting a strap fastened to the bit): from Old French courber 'bend, bow', from Latin curvare (see curve)

Do not confuse curb with kerb. Curb means 'control or limit something' ( she promised to curb her temper) or 'a thing that controls or limits', whereas kerb means 'the stone edging of a pavement' (the spelling curb in this sense is American).