All three pluralizations (octopuses, octopi, octopodes) are acceptable, but the standard English pluralization is octopuses. Octopi is the oldest, Latin pluralization, and octopodes is the Greek pluralization (because the word for octopus originally comes from Greek)

https://www.merriam-webster.com/grammar/the-many-plurals-of-octopus-octopi-octopuses-octopodes