The Spanish word 'culo' (meaning 'buttocks') comes directly from the Latin word 'culus', which had the same meaning of 'posterior' or 'buttocks'. This is a straightforward inheritance where both the form and meaning have remained remarkably stable from Latin to modern Spanish, with only minor phonological changes typical of Spanish evolution from Latin.

Some common Spanish words derived from the same root include 'culero' (diaper or nappy) and 'culata' (buttstock of a firearm), both of which maintain a connection to the original anatomical meaning.

While English doesn't have many common cognates from the Latin 'culus', there are some scientific terms like 'culet' (the bottom facet of a cut gem) and anatomical terms that preserve this Latin root. The word 'cullion' (a vulgar term for testicles) is a distant relative, though it's now archaic.