"Coup" and "coup d'ètat"

Coup /ˈkuː/ is sometimes used as a shortened form of coup d'état /ˌkuːˌdeɪˈtɑː/  in English -- but it sometimes has a different meaning.

Coup d'état  means "a sudden attempt by a small group of people to take over the government usually through violence."

One sense of coup is simply a shortened form of coup d'état:

a military coup

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But in its second sense, coup means "an impressive victory or achievement that usually is difficult or unexpected":

It was a major coup when the team traded for the star pitcher.

I found a valuable rare book at the yard sale -- what a coup!