The Spanish word 'piel' meaning 'skin' comes directly from the Latin word 'pellis', which meant 'skin' or 'hide'. The evolution from Latin to Spanish shows a typical sound change where the double 'l' simplified and the vowel 'e' developed into 'ie', a common diphthongization pattern in Spanish.

Some related Spanish words include 'pelar' (to peel), 'película' (film/movie - literally a thin skin or layer), and 'pelaje' (fur/coat of an animal). All these words share the same Latin root and maintain connections to the concept of skin or outer covering.

English speakers might recognize this connection in words like 'pelt' (animal skin), 'peel', and even 'film' (which, like Spanish 'película', can refer to a thin layer or skin). The word 'pelage' (an animal's coat) is also related. All these words trace back to the same Latin root 'pellis'.