The Spanish word 'loco' meaning 'crazy' or 'mad' has an interesting origin in Arabic. It comes from the Hispano-Arabic word '*láwqa' meaning 'stupid', which itself derives from Classical Arabic 'lawqa'' (feminine form) also meaning 'stupid'. This is one of many Spanish words that entered the language during the centuries of Arabic influence in medieval Spain. The meaning evolved slightly from 'stupid' to the modern sense of 'crazy' or 'mad'.

Some common Spanish words and expressions derived from 'loco' include 'enloquecer' (to drive crazy/to go crazy), 'locura' (madness/craziness), and the colloquial phrase 'estar loco por' meaning 'to be crazy about' something or someone.

While there aren't direct English cognates of 'loco' since it comes from Arabic rather than Latin roots, the word 'loco' itself has been borrowed into English slang, particularly in the American Southwest, where it's used with the same meaning as in Spanish. You might also recognize it from English compounds like 'locomotion' or 'locomotive', but these are actually unrelated - they come from Latin 'locus' meaning 'place'.