One of my friends argues with me that the plural for etiquette is etiquettes and for fish it is fishes. I was taught since ever that etiquette is plural as fish does. To support his statement he showed some references of word "fishes" in novels and magazines, however, he couldn't find "etiquettes" anywhere that I would accept (www.morewords.com/word/etiquettes and wiktionary). The disagreement remained because in his argument, he says the word came from french where it is measurable/countable, so should be in English. My argument is that it is just a derived word and does not mean the exact same thing, etiquette in English is not countable/measurable. Or is it?
If he is correct, may I please be provided with some solid references?