The French and Spanish words are from Latin gryllus 'cricket' which was borrowed from Greek γρυλλος (grullos), where it means a dancer of γρυλλισμος (grullismos) 'an Egyptian dance'. Intreaguin, too, is that γρυλος, with long ypsilon and single lambda, is a word for 'pig, porker'. The word is said to be of obscure origin because it has not been tracked back to other languages. One would have to explain why Latin -ll- went to /j/ or /ʎ/ inthose languages, but to /g/ in English. And, which language did English borrow it from?

Ceci n'est pas un seing.