The correct spelling of the plural of potato is spuds!!
The serious answer is potatoes as words that end in an 'o' that are preceded by a consonant are usually (but not always) turned to plural by adding "es" eg tomatoes, torpedoes and of course potatoes. A couple of exceptions to this rule are Eskimos, and pianos.
I thought Dan Quayle couldn't spell the singular form of potato.
All languages are constantly developing and evolving, words are added, others fall out of use and some existing words are given new meanings.
In looking for changes made by historical events and social pressure you only need look at difference between American English and British English which started from a common starting point yet were split by the American War of Independence.