Mid 18th century (denoting something designed to elicit applause): from clap¹ + trap¹.

• poppycock from mid 19th century:

  The English language has any number of curious words for ‘nonsense’, such as balderdash (late 16th century) of unknown origins, and codswallop, claptrap—first used in the modern sense by Lord Byron, and piffle (mid 19th century) from the sound. Poppycock was originally Dutch, and comes from pappekak, which meant either ‘soft dung’ or ‘doll's excrement’ Another such term is bosh, a Turkish word meaning ‘empty, worthless’ which was popularized by its frequent use in James Morier's highly successful 1834 novel Ayesha, the Maid of Kar.