It is said that long time ago, in the Hetao area of the Yellow River, there were neither bridges nor boats, so people usually used rafts made of cow skin, which was referred to ‘cow skin raft’ later. After being blown with enough air, the raft will be able to drift on the water with people onside.

"Blowing cow skin raft" is a very laborious task, which generally needs several people to work together in order to inflate a skin raft. Therefore, people began to describe those who like to brag as ‘he can blow a cow skin raft full’. In this way, ‘blow cow skin raft’ is linked with brag. Over time, "blow cow skin raft" finally turned into a synonymous of "brag".