"thump your chest"

What does "thump your chest" mean?
e.g. It may be smart to thump your chest and critize your friend.

Actually, it may be *hypocritical* to thump your chest while criticizing your friend. In the old days (pre-1965 or so), when Roman Catholic Mass was in L@tin, the congregation would say together "Mea cula, mea culpa, mea maxima culpa", while striking the chest three times. The phrase means roughly "I have sinned, I have sinned, I have sinned terribly".

Culpa means fault, guilt or blame, as in culpability or exculpate.

So mea culpa is "my fault, my fault, my most horrendous fault".

You are always at fault in Catholicism, the result of being born into sin and they ( top management ) don't let you forget it.

I think of that stuff as "breast-beating." I thnk of "Chest thumping," on the other fist, as the stuff that apes (and, um, Tarzan) do to bellow in a testosterone-soaked intimidation ritual. Self-assertion on steroids.