But your chart says it's only used in foreign words. Apparently it's not a natural sound in Hindi. Surely you learned that pronunciation from the British long before the first Mexican ever showed up in India to explain how it's supposed to sound. We say it that way too. Well actually it's MEX-ih-ko over here. But we're not consistent. We pronounce José as ho-ZAY instead of kho-SEH, and Juan is just WAN, like the adjective, instead of KHWAN. The word doesn't appear in American dictionaries. Wikipedia says the meaning of "insane" came about because being stationed at the British Army transit camp in Deolali was unbearably boring.