This is a phrase that combines the image of an eagle with the concept of an oath or promise that is transitory or temporary. It suggests a commitment or pledge that is not enduring but, instead, symbolizes the impermanence of life and the fleeting nature of certain things. In this context, it could imply the idea that life and its experiences are beautiful and meaningful, but they are also temporary and subject to change. The term blends the strength and majesty of the eagle with the idea that even powerful and majestic creatures are bound by the ephemerality of life.