In his younger days, Gazlowe was a thief, like many goblins. Through adventuring, he gradually managed to make enough money to begin legitimate business, and proved to excel at it.
After the Third War, he was hired by Thrall as the chief engineer to help securing a reliable source of water for the newly constructed Orgrimmar city. Gazlowe sent an expedition to dig out some tunnels beneath the city, they looked for underground wells for use in the newly founded city, but they accidentally tunneled into a den of kobolds who immediately flooded into the caves and drove the goblin mining teams into retreat.
Later, when Rexxar was looking to earn his keep in Orgrimmar, Gazlowe sent him into the dug tunnels, the Orgrimmar Tunnels, to help collapse the offshoot tunnels which the kobolds were using. Gazlowe and his engineers also dug out other tunnels where they found an unexplored city, they call that place Gazlowe's Excavation Site.