why is it called holloween "H2O"?

This movie is meant to be a sequel to "Halloween II". The "H20" refers to it taking place twenty years after the original "Halloween". It was also made 20 years after the first one was made.

it it called h20 becuase jamie curtis came up the with the idea of that movie she thought that she would call it that because it would have been 20 years to the date that it came out that she has been in the movie business

halloween twenty years later

Halloween H20 means Halloween 20 years later but it's been shortened to H20.

2o years later