https://www.merriam-webster.com/words-at-play/the-many-plurals-of-octopus-octopi-octopuses-octopodes https://www.merriam-webster.com/words-at-play/the-many-plur

https://www.merriam-webster.com/words-at-play/the-many-plurals-of-octopus-octopi-octopuses-octopodes https://www.merriam-webster.com/words-at-play/the-many-plura... The full thing is worth a read, but when you steal a word from one language that it also stole from a third, the pluralization rules are pretty much anything goes.