<P> Having to choose whether to have or eat your cake illustrates the concept of trade - offs or opportunity cost . </P> <P> The order of the clauses in the saying has been the subject of some debate, and was even used in forensic linguistics (contributing to the identification and arrest of the so - called Unabomber). </P> <P> An early recording of the phrase is in a letter on 14 March 1538 from Thomas, Duke of Norfolk, to Thomas Cromwell, as "a man cannot have his cake and eat his cake". </P> <P> The phrase occurs with the clauses reversed in John Heywood's "A dialogue Conteinyng the Nomber in Effect of All the Prouerbes in the Englishe Tongue" from 1546, as "wolde you bothe eate your cake, and have your cake?". In John Davies' "Scourge of Folly" of 1611, the same order is used, as "A man cannot eat his cake and haue it stil ." In Jonathan Swift's 1738 farce "Polite Conversation", the character Lady Answerall says "she cannot eat her cake and have her cake ." </P>

Where did have your cake and eat it too come from