Ossify means to become bony. When a baby is born, some of their "bones" are actually soft cartilage, which allows for growth. As the child grows, these soft areas ossify into actual bone. The knee cap, for example, begins to ossify between ages 3 and 6.
From the literal "to become bony" meaning of ossify, we get the more figurative meaning: to become rigid or hardened. Although you and other young people may be willing to effect social changes, many older voters have ossified in their opinions. Convincing these rigid thinkers that these changes are good for the country will be quite the challenge. If your kids sneak food to their rooms, you may find ossified cheese under the beds. Even mice won't touch that!