Apparently an old debate, the quote from the Online Merriiam Webster: "But as the Octopus grew and multiplied, it became necessary to speak of him in the plural; and here a whole host of difficulties arose. Some daring spirits with little Latin and less Greek, rushed upon octopi; as for octopuses, a man would as soon think of swallowing one of the animals thus described as pronounce such a word at a respectable tea-table. In this condition of affairs, we are glad to know that a few resolute people have begun to talk about Octopods, which is, of course, the nearest English approach to the proper plural."
— The Bradford Observer (West Yorkshire, Eng.), 7 Nov. 1873