My inclination when preparing my earlier post on “avocados” was to spell the plural as “avocadoes”. After all, it’s “tomatoes” and “potatoes”, and, just like avocados, they get eaten. But the spell-check insisted – no “e”.
But why is this so? I consulted my Fowler’s Modern English Usage (my copy is 2nd ed, for those who need to know). Needless to say, there’s no entry under “avocado”. However, there’s an entry for “-o(e)s”. As is usual with Fowler, the commentary was fascinating! But shortly stated, it seems that although there are a lot of nouns ending in “o”, in fact only a minority have “oes” in the plural form. But many of the familiar words with this ending do go this way in the plural firm, such as “potato”, “cargo”, “hero” and so on.
Hence “oes” at first sight often seems “right” to us. But in fact it’s quite correct for other words to be just “os”, such as “infernos”, flamingos” and “embryos”. Fowler suggests that in some cases, words that aren’t often used in the plural form tend to use “os”.
In the case of “avocado” (which is used a lot as a plural!), there’s also an explanation here along the lines that the founders of the California Avocado Association actually told the dictionary publishers that the plural didn’t have an “e”. I guess that’s your right, when you’re promoting a name for a something (as the article claims the Californians did). However, Wikipedia doesn’t give all the credit for the word itself to the Californians, saying that it’s derived from the Spanish. which is also stated in the Macquarie Dictionary.