The story
From the University of Alabama's fight song Yea Alabama, which ends in the words “Go, roll to victory, Hit your stride, You're Dixie's football pride, Crimson Tide! [Roll Tide, Roll Tide!]”.
Etymology from Wiktionary, CC BY-SA 4.0.
roll tide
Today it means: An all-purpose term of enthusiasm in support of the University of Alabama football team. Full definition →