The Spanish word 'casta', meaning 'caste, breed, or lineage', traces its origins back to Proto-Germanic 'kastuz', which meant 'heap' or 'group'. This term evolved into Gothic 'kasts', meaning 'group' or 'collection', before eventually making its way into Spanish. The semantic evolution from a general notion of a 'group' or 'heap' to a more specific meaning of 'breed' or 'lineage' reflects how the word came to be used for classifying and categorizing different groups of people or animals.

A common related Spanish word is 'castizo', which means 'pure-blooded' or 'of good lineage'. This term derives directly from 'casta' and was historically used to refer to people of pure Spanish descent. Another related word is 'encaste', which refers to a breed or strain, particularly in the context of fighting bulls.

The English word 'caste' is directly related to the Spanish 'casta', though it entered English through Portuguese. Like its Spanish cousin, it refers to a system of social stratification. The English term 'cast' (as in 'casting lots' or 'cast of characters') also shares distant Germanic roots with 'casta', reflecting the original meaning of a group or collection of things.