“Arms” has the same two meanings as in German (see e.g. the College of Arms — hint: it’s not a place where they teach weaponry). “Coat” in this context refers t

“Arms” has the same two meanings as in German (see e.g. the College of Arms — hint: it’s not a place where they teach weaponry). “Coat” in this context refers to the actual coat worn by heralds representing the sovereign. The modern word for that outfit is “tabard” I believe.