Note 529 — ACT IV., SCENE I.
Reading edition
A common expression in old writers, indicating that some party has not been treated with sufficient respect. M is short for Master, and Frisco addresses himself to the Bellman, who had merely called him Frisco. Thus, in "Eastward Ho!" act iv. sc. 1, Quicksilver asks, "Must Golding sit upon us?" To which the constable replies, "You might carry an M under your girdle."