Why was gruel called gruel?

Gruel is a dish made from coarse meal or oatmeal boiled in water or milk. The name "gruel" is derived from the Old English word "grytt" which means "grain". The word "gruel" was first used in the 14th century to describe a type of porridge made from wheat meal. The term was later used to refer to other types of porridge made from oatmeal, cornmeal, or rice.