The Spanish word 'poto' meaning 'buttocks' has interesting origins in indigenous South American languages. It can be traced through a chain of related words: from the Mochica word 'potos' meaning 'genitals', to the Quechua 'putu' meaning 'vessel', and then to the Mapudungun word 'poto' meaning 'bottom' or 'base'. The meaning evolved from specific body parts to a container shape to a general term for the bottom part of something, before settling on its current Spanish meaning of 'buttocks'.

This etymology shows how words can travel between different indigenous languages of South America and eventually make their way into Spanish, with meanings shifting but remaining connected to the general concept of lower parts or rounded shapes.

Since 'poto' entered Spanish from indigenous American languages rather than from Latin or Greek roots, there aren't many simpler or more common Spanish words that share its etymology. This makes it a somewhat unique word in Spanish vocabulary.

There aren't any common English words directly related to 'poto' since it comes from indigenous American languages rather than the Indo-European roots that English and Spanish often share. English speakers would need to learn this word independently rather than being able to relate it to familiar English terms.