Fears are a normal part of childhood. Certain fears are typical at certain ages. Fear is real to your child, so take your child's fears seriously.
Some fears develop with independence.
For example, when a child begins to walk and understands he can leave mom, he realizes mom can leave him as well. A child's surroundings can increase fears, such as unfamiliar places, crowds, shadows from night lights, etc. Sometimes a child's fear is based on a lack of knowledge. The water goes down the drain, so I might disappear down the drain. Often, a child's fears are the same as his parent's.