Mario is known as a plumber and can be a representative for the profession. Although that was not his first job, his first work was as a carpenter. This was rationalized as the levels took place at construction sites. His name was also different, he was first known as Jumpman as he made his way up, dodging barrels to get to Pauline and free her from Donkey Kong.
He was named Mario after Mario Segale, who was the landlord of the Nintendo of America warehouse. The president of Nintendo at the time, Minoru Arakawa owned back rent to him. Arakawa convinced him that he would be paid and opted to name the character Mario in the new game instead of Mr. Video which was the first suggested name. The new game would have underground levels which the character would get to using pipes. Thus, Mario became a plumber and a hard working common guy who traveled through the sewers of New York City. Due to the hardware restrictions at the time Mario was made with the contrasting red and blue clothing so that he would stand out. The hat was added so they wouldn’t having to design the hair, forehead, and eyebrows. To make him appear human they a gave him the large nose and mustache. The Mario character that we all know and love was created, and he remains a symbol of Nintendo, video games, and plumbing.
Here is a detailed picture of Mario that has developed over the coarse of Mario history.