the.com/coat of arms

means A unique heraldic emblem, traditionally passed down through a family or granted to a person or institution, displaying symbols that once identified knights and now mostly identify rich ancestors.

from From the actual cloth coat — the 'surcoat' — that medieval knights wore over their armor, painted or embroidered with their heraldic design so allies could identify them in battle when their face was hidden behind a steel helmet. The 'coat' came first; the 'arms' (from Latin arma, meaning weapons or equipment) referred to the whole heraldic package of shields, colors, and symbols a knight fought under. Over time the coat rotted away but the name stuck to the design itself.