The Spanish word 'asco' (meaning 'disgust') has an interesting journey from Ancient Greek through Latin. It starts with the Greek word 'eskhara' (ἐσχάρα), which meant 'hearth' or 'scab'. This word was borrowed into Latin as 'eschara', specifically meaning 'scab' or 'crust'. From this, Latin developed the adjective 'escharosus' meaning 'scabby' or 'crusty'. This evolved into Spanish 'asqueroso' ('disgusting'), from which the noun 'asco' was derived through a process called back-formation. The semantic evolution from 'scabby/crusty' to 'disgusting' and 'disgust' is quite intuitive, as things that are scabby or crusty often provoke feelings of revulsion.

The most common related Spanish word is 'asqueroso' (disgusting, revolting), which is actually the source word from which 'asco' was derived. If you know the adjective 'asqueroso', you can easily remember that 'asco' is the feeling of finding something asqueroso - that is, the feeling of disgust itself.

While there aren't many common English cognates, the medical term 'eschar' (meaning a scab or dead tissue resulting from a burn or infection) comes from the same Greek root 'eskhara'. This preserves the original meaning of the word before it evolved to describe the feeling of disgust in Spanish.