You can't cod me. / I was only codding.
You can't fool me. / I was only joking.
Irish 'Cadar√°il' - foolish prattling. (Dineen) English - nonsense, hoax, parody, from 'cods-wallop' (origin unknown). (Concise Oxford Dictionary) To chaff, hoax, play the fool. (Partridge) Nore 'Codderauling' - idle gossip, prattle. (√ď h-√Čaluithe) and see 'Who are you codding?'. (O'Mahony)