Today's Maven's word of the day is "ruckus" and it discusses how to pluralize said word (whether it's ruckuses or rucki). They cite octopus as a word that, like ruckus, ends in -us but does not take the -i ending in the plural.

AHD gives this etymology: New Latin Octps, genus name, from Greek oktpous, eight-footed and offers the plural as octopuses or octopi.

Perhaps it's not -i'd because it's from the Greek, and is New Latin (I assume this means Latin words coined in modern times by taxonomists and others scientific types - is this correct?).

Prior to reading this, I'd have been tempted to correct anyone saying octopuses. Who of y'all says which?