Plural Octopus

I learned recently that I have been saying the plural of octopus incorrectly for many years. Apparently the word octopus originated from the Greek oktṓpous. The correct plural of this is octopodes; many incorrectly assume that the word is Latin, which would result in a plural of octopi. Currently most people accept octopi or octopuses as reasonable, especially as octopodes are rarely encountered, as the octopus is a mostly solitary creature. 

Image from: XKCD