Knacker \Knack"er\, n.

1. One who makes knickknacks, toys, etc. --Mortimer.

2. One of two or more pieces of bone or wood held loosely between the fingers, and struck together by moving the hand; -- called also clapper. --Halliwell.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Clapper \Clap"per\, n. [F. clapier.]

A rabbit burrow. [Obs.]

Source: Webster's Revised Unabridged Dictionary (1913)
 

Clapper \Clap"per\, n.

1. A person who claps.

2. That which strikes or claps, as the tongue of a bell, or the piece of wood that strikes a mill hopper, etc. See Illust. of Bell.

Clapper rail (Zo["o]l.), an Americam species of rail (Rallus scepitans).

Source: Webster's Revised Unabridged Dictionary (1913)