Well, the whole expression basically means "we'll show you who's who". It became famous after Soviet leader Khrushchev while having an official conversation with Americans took off his boot, hit the table with it and shouted, "мы вам покажем кузькину мать!"
Hmmm, the version I'm familiar with is that Khrushchev did this at a UN meeting, and he shouted to the Americans "Мы вас похороним!"

The Russian phrase was (correctly not INcorrectly) translated into English as "We will bury you," but Americans understood the meaning to be "Мы вас погребём заживо!" ("We will throw you in a hole and bury you while you're still alive" -- as happened in more than one Edgar Allen Poe story, or as the man did to Uma Thurman in Kill Bill 2!)