Nothing is known with certainty about Garrison's early years, but it is generally believed that he was orphaned at a young age. At 13, he joined a local gang called the Turks. By the time he turned 18, in 896, he had risen to become the gang's leader. In 899, when gangs first began organizing inter-village alliances (most notably LandOrder and InterGang), the various Prittian gangs began an all-out war among themselves for total dominance within their village, to determine which of them would have the honor of joining one of the inter-village gangs. In 900, while the gang war in Pritt was still ongoing, several gangs from Kurok banded together and relocated to Pritt, having come under ever-increasing constraint by the Kurokish police. The Kurokish gangs believed that the war must have severely weakened the gangs of neighboring Pritt by that point, which would make it easy for them to take over. However, Garrison responded to the invasion by uniting the Prittian gangs under his leadership, to repel the outsiders. He became famous for having said, "Are we gonna let our village get taken by a bunch of interlopers who were run out of their own town by the police?" The question was considered highly derisive by Prittian gangsters, as their war had proven more than their village's police could handle, rendering the Pritt PD increasingly ineffective. This was seen as a clear indication that Prittian gangsters must be tougher than Kurokish gangsters, and is credited as one of the main reasons former enemies were willing to band together under Garrison.
After defeating the Kurokis, Garrison entertained emissaries from both LandOrder and InterGang. It is commonly said that he decided to pledge his gang to LandOrder simply because InterGang had recently acquired a branch in Olek, on the southernmost of the East Isles, and that he thought it would be "symmetrical" for LandOrder to have a branch on the northernmost of the Isles. It is unknown whether this alleged reasoning is truly why he chose LandOrder.
In 905, when the first census-takers approached him and asked what surname he'd chosen (per the surname law, which had been enacted the previous year), Garrison is reported to have responded only by holding up his middle finger. Thus, they assigned him the name "Finger." It is said by those close to him that when he later learned of the surname he'd been given, he laughed and said, "Not bad. Yeah, I like it."