The Spanish word 'tuto' meaning 'sleep' (used in baby talk or childish language) comes directly from the Mapuche language word 'tuto' which also means 'sleep'. This is one of several words that Spanish has borrowed from indigenous South American languages, particularly in regions where Mapuche people lived, like Chile and parts of Argentina. The word maintains both its pronunciation and meaning from the original Mapuche, though in Spanish it's specifically used as a childish or affectionate way to refer to sleep, similar to how English speakers might say 'beddy-bye' or 'sleepy time' when talking to children.

Since 'tuto' entered Spanish directly from Mapuche, there aren't any simpler or more common Spanish words that share its etymology. Most Spanish words for sleep, like 'dormir' or 'sueño', come from Latin origins and are not related to this indigenous loanword.

There are no etymologically related English words to 'tuto', as it comes from the Mapuche language of South America. English and Mapuche developed completely independently of each other, belonging to entirely different language families.