The Spanish slang word 'guay', meaning 'cool' or 'great', has an interesting origin that traces back to Arabic. It comes from the Arabic word 'kuwayyis' (كويس), meaning 'good' or 'beautiful'. The word entered Spanish as 'guais' and eventually evolved into the modern form 'guay', maintaining its positive connotation but taking on a more colloquial, slangy feel in modern Spanish usage.

Since 'guay' entered Spanish directly from Arabic and evolved specifically as a slang term, there aren't many common Spanish words that share its etymology. The older form 'guais' might still be heard in some regions, but 'guay' is the standard modern form of this slang expression.

There aren't any common English words directly related to 'guay' since it comes from Arabic and entered specifically into Spanish. However, English speakers might find it helpful to remember that 'guay' is used very similarly to how we use 'cool' in English as a slang term for something good or great.