The Collaborative International Dictionary of English v.0.48:

Clicket \Click"et\, n. [OF. cliquet the latch of a door. See 5th
   Click.]
   1. The knocker of a door. [Prov. Eng.]
      [1913 Webster]

   2. A latch key. [Eng.] --Chaucer.
      [1913 Webster] clickety-clack