McGruder is a surname that refers to:
McGruder is a Scottish name related to McGruther, McGrouther, etc. and appears most often in USA as Magruder. The first USA immigrant John, who became the founder of the American Magruders, originally spelled his name McGruder. There are many phonetic variations of the name, including McGrowther, Mcgruar, McGrudder, etc. Wha's like us?/MacGrouthers in Scotland before 1855/McGruders in America by Sue Emerson & Don McGruther
References
McGruder Wikipedia(Text) CC BY-SA