Graduated Payment Mortgage
Think about someone graduating. First, there's preschool graduation. Then fifth-grade graduation, elementary school graduation, junior high graduation, high school graduation, and college graduation. Education level getting higher each step.
Apply this to mortgage payments. The amount getting higher at each step. Graduated.
A GPM is like an introductory trial period for owning your house. Mortgage payments start off relatively small in the beginning, then rise over time. Eventually, they reach the full monthly payment of a traditional mortgage.