October means the eight month - it's now the tenth. November means the ninth month - its now the eleventh. December means the tenth month - it's now the twelfth. Write down other words based on Roman number names eg octagon, octopus, monocle, bicycle , decimal etc. Based on the pattern of daylight and darkness - which repeats itself in about the time it takes the Earth to spin round once on its Axis.
Different authorities suggest different reasons.
There are many variations of this rhyme, several more can easily be found on the web by using a search engine. More able children could invent there own rhyme about the months of 1752. Consider other ways of distributing 365 days between 12 months, or of dividing up the year. Since ancient times, people from many parts of the world have divided the day into 24 hours. No one knows why the number 24 was chosen - it may have been to do with the appearance of certain bright stars in Egypt.