The origin of the expression "haber gato encerrado" comes from ancient times when people wore "monederos" (change purses) which were made from cat skin and they hid them underneath their clothes to protect their money from being stolen. So literally, "the cat was hidden." Another definition for the word "gato" also included in the dictionary is "bolsa para guardar dinero".
Dar mala espina, is another common expression whose meaning is very similar to haber gato encerrado. Literally, To give a bad thorn, has no meaning at all, but figuratively it is said when someone has the feeling that something is wrong and suspects that he or she could be the victim of a scam, and somehow could get into trouble. If for example, you are about to purchase a very expensive work of art which the art dealer assures you that is a unique and authentic piece from the Roman times, and then you see a small label at the back that says: "Made in Spain." In this scenario, one can say: Me da mala espina. - I smell a rat!
Ejemplo 1:
He recibido un email que dice que puedo ganar un viaje a la República Dominicana gratis si compro tres libros. ¡Me parece que aquí hay gato encerrado!I've got an email saying that I can win a trip to Dominican Republic if I buy three books. I think there's something fishy here!
Ejemplo 2:
La bruja camuflada de vendedora ambulante le dijo al niño que fuera a su casa porque allí tenía caramelos pero el niño sabía que había gato encerrado y no fue con ella.The witch disguised as a street vendor told the kid to go to her house because she had candy but the kid knew there was something fishy and didn't go with her.
Ejemplo 3:
Mucha gente dice que hay gato encerrado con el hecho de que Brasil tenga el Mundial de fútbol en 2014, la Copa America en 2015 y los Juegos Olímpicos en 2016.Many people say that there is something fishy with the fact that Brazil is hosting the World Cup in 2014, the America Cup in 2015, and the Olympic Games in 2016.