In the movie Iron Man, why is Iron Man naming his suits as "Mark 1, Mark 2, Mark 3" and so on. how did he came up with that Name?
"Mark" used in this way isn't a name; it's a synonym for "model" or "version". According to Wiktionary, the relevant definition is
A famous usage of this nomenclature was in the naming of the Colossus Mark I and Mark II computers, used in code-breaking during World War II.