This is not a slang term but a common saying in Spanish, which translates to 'A liar should have a good memory'. It means that if you lie, you should remember your lies to maintain consistency and avoid getting caught.
Examples
- Spanish: No te conviene mentir sobre tus calificaciones, recuerda que 'el mentiroso debe tener buena memoria'.
- English: It's not a good idea to lie about your grades, remember that 'a liar should have a good memory'.