Perhaps the most common Spanish word for pillow is
almohada, but Costa Ricans tend to use
cabecera for the pillow that you sleep on. This word should not be confused with
cabezazo, which is a header (when you strike the soccer ball with your head).
A funny expression that I picked up in
Costa Rica was
planchar la oreja, or iron the ear, which one would say before going to bed.
Example: "Tengo sueño. Voy a planchar la oreja."