TIGERS is painted in their end zone. I reckon War Eagle is like the second name for the Alabama Pachyderms - Crimson Tide.
According to the Auburn website, nickname is and has always been Tigers.
They were referred to as "Plainsmen" in the past as they were indeed plainsmen.
War Eagle comes from the fact that their mascot is a Golden Eagle and the term "War Eagle" is a cheer. The current eagle #vII is named Nova.