Jesus is called "the Lion of Judah" as a reference to his family lineage and power. The Tribe of Judah is often symbolized by the lion.
The first reference between the Tribe of Judah and a lion occurs in Genesis, when Jacob offers a prophesy related to Judah. The prophesy points to the everlasting kingdom of Jesus.
In the book of Revelation, Christ is called the Lion of Judah and the Root of David as reference to both his family line and his triumph. Another interpretation of the connection to the lion comes from medieval literature, which suggests that the lion represents resurrection. The literature goes on to suggest that a lion cub is brought to life on the third day after its birth by its father.