Change description of iCloud Account?

[MikeV99]

On my iPhone 6P I was able to change the name of the iCloud in settings from iCloud to Mike's iCloud. Unfortunately, I do not remember how I made the change. I have setup my wife's iPhone 6P but am not able to figure out how to change her account from iCloud to Mary's iCloud. (As an aside, I have changed the description of her iCloud account on my MBA and iPad/iPhone devices.) Any ideas how to make the change? Thanks.