potam(potham) means group of people telling that they want to go. example: we want to go movie. we want to go out. when "m" added to "potha" it indicates group of people wish to go. example for "potha". I want to go. I hope you will understand.

Pottam means we are going pothanu / potha means i am going the above two words may be originated from povatam which means going and its oposite ravatam which means coming