One who or whatever limits a boundary
- somebody who is morally reprehensible
- an individual who bounds or leaps (as with competition)
- One who, or what, restrictions; a boundary.
1560s, "one who establishes bounds," agent noun from certain (v.1); Uk English slang indicating "person of objectionable social behavior, potential fashionable individual," is from 1882, possibly from bound (v.2) on notion of just one attempting to "bound" into high society, but very first usage proposes one beyond your "bounds" of acceptable socializing, which would connect it aided by the noun.
(letter.) Person who, or that which, limits; a boundary.