How Well Do You Know English Slang?
c.1730, "trick to 'catch' applause," a stage term; from clap (v.) + trap (n.). Extended sense of "cheap, showy language" is from 1819; hence "nonsense, rubbish."
Nonsense; mendacious cant; bullshit
[1819+; fr early 1700s theatrical use, literally ''a trap toget a clap,'' a device, verbal or otherwise, for milking applause]