The King Samhain story is a complete and utter fabrication that mocks Celtic culture. Samhain is Irish New Year (before Christianity) and means literally "in the belly" referring to the fact that this is the final harvest and what you will have to eat, because frost and rain will destroy what remains in the field. This is no folklore nor history about a King Samhain. The reason we have Cthulhu and the Flying Spaghetti Monster is so we can have fun stories but not show contempt for genuine religious traditions. People who male up crap about Ishtar, Osiris, Zeus, etc. are religious bigots and deserve criticisms by polite, well mannered people, and this education begins with children. All the aforementioned deities still have worshippers, so it is no different that publishing stores about "Jesus the Zombie" or "He hides from the Sun in the Ark and drinks blood: Jehovah the Vampyre". Looks different when your own toes get stomped on, doesn't it? Be done by as you do to others.

I get it being a way to say the title but what does it mean being in the movie?

It is commonly stated that the second movie takes place 5 years after the events of the first movie, but this is not accurate. In GB1 , a banner on City Hall indicates that the year is 1983. In GB2, the calendar on Dana's apartment wall says it's November 1989. 6 years, not 5.