The Spanish verb 'guayar' comes from combining the noun 'guayo' (a type of thorny tree) with the Spanish verb suffix '-ar'. The word 'guayo' itself comes from Mapudungun 'wayu', meaning 'thorn' or 'thorny tree'. The verb 'guayar' developed to mean 'to scrape with a guayo', likely referring to using the thorny parts of the tree as a scraping tool.

A simpler related Spanish word is 'guayo', which refers to the thorny tree itself. This noun is more basic than the verb 'guayar' and might be encountered first by Spanish learners.

There are no common English words directly related to 'guayar' since it comes from Mapudungun, an indigenous language of Chile and Argentina, rather than from Indo-European roots shared with English.