"The name which he afterwards acquired being doubtless due to the peculiarity of his personal appearance, the largeness of his head. Matthew Paris speaks of him as "Robert who is known by the surname of Grosseteste," or "Robert called Great-Head." Nicholas Trivet says, "he was surnamed by many Great-Head.""
January 1, 1970
https://en.wikiquote.org/wiki/Robert_Grosseteste