OK, I am googling in addition to relying on the collective knowledge of the group, of interest to Brit car trivia buffs--this entry in the Wiki about Booker T. and the MGs (whose hit, Green Onions is great garage and or drving music by the way):
"The exact origin of the band's name is a matter of dispute. Booker T. Jones has stated that it was Jackson who named the group after its youngest member. "M.G." is supposed by many to refer to "Memphis Group," not the sports car of the same name.[6] However, musician and record producer Chips Moman, who was active in Stax Records when the band was formed, claims that they were named after his car, and that it was only after he left the label that Stax's publicity department declared that "M.G." stood for "Memphis Group". To lend some credibility to this story, Moman had played with Booker T. Jones in an earlier Stax backing group named the Triumphs, also after his car.[7] Steve Cropper has also endorsed this explanation."
MG and Triumph references--cool!