Example: Shana’s been fooling around with cars since she was a kid. She cut her eyeteeth on them.
Meaning: to acquire wisdom; to gain valuable experience, often at a young age.
Origin: When a baby’s first teeth start growing in, the teeth are actually cutting through the gums. Children also chew on things in order to help new teeth break through the gums. Years ago the analogy of cutting teeth and having experiences early in life probably led a writer to create this expression. We think eyeteeth got their name because they are right under the eyes in the upper jaw. But no one knows why eyeteeth are mentioned in this expression since they’re not the first teeth to grow in. Sometimes the saying is shortened to “cut your teeth” on something.
Source: Scholastic Dictionary of Idioms by Marvin Terban