On the original U.S. TV series "Star Trek", Scotty is a fictional character his first name is Montgomery. He was first portrayed by James Doohan. Later, he was in the 1973 - 74 animated "Star Trek" series, seven "Star Trek" movies, the "Star Trek: The Next Generation" episode "Relics", and in numerous books, comics, and video games.

From the TV show, we learn that Scotty (the fictional Lt. Commander Montgomery Scott) was born on March 3, 2222, and spent part of his life in Aberdeen, Scotland. He wears Clan Scott's tartan as part of his dress uniform and he has a strong Scottish accent obtained from ancestors from the Highlands.

During events on "Star Trek", Scotty holds the rank of lieutenant commander and serves as the Enterprise's 2nd officer and 'miracle worker' chief engineer. He will command the ship and record its log when both Captain James T. Kirk (William Shatner) and 1st Officer Spock (Leonard Nimoy) are not aboard. Scotty's technical knowledge and skill allow him to devise unconventional and effective last-minute solutions to dire problems. Scotty's identity is strongly connected to the Enterprise itself, and the character often takes a paternal attitude toward the ship. He is frequently the liaison between Captain Kirk's ambitious tactical plans and what is technically feasible in the realm of the starship's capabilities.

Scotty said in the TNG episode "Relics", "He never wanted to be anything else but an engineer".

More Info: en.wikipedia.org