‘To be swamped’ is a common idiomatic expression that means to be overworked or to have too much work to do. The expression comes from the word ‘a swamp’ which is an area of land coverd by water but where trees and plants grow. In Louisiana, they call this the bayou.
Here are some example sentences :
Online bookstores were swamped with orders during the pre-Christmas rush.
I can’t take this new project because I am swamped.