The Spanish word 'nahual' comes directly from the Nahuatl (Aztec) word 'nahualli', which meant 'sorcerer' or 'wizard'. In Mexican folklore, a nahual refers to a person who has the ability to transform themselves into an animal, or to their spirit animal companion. This concept was deeply rooted in pre-Columbian Mesoamerican beliefs and continues to be an important part of some indigenous Mexican cultures today.

Since 'nahual' comes from Nahuatl, an indigenous Mexican language, rather than from Latin or Greek like many Spanish words, there aren't many common, simpler Spanish words that share its etymology. However, you might encounter related terms like 'nagual' (an alternative spelling) or 'nahualismo' (the practice or belief system involving nahuales) in discussions of Mexican folklore and spirituality.

There aren't any common English words directly related to 'nahual' since it comes from Nahuatl. However, English has borrowed this word as 'nagual' with the same meaning, though it's primarily used in anthropological or folkloric contexts when discussing Mesoamerican spiritual beliefs.