why tetris called tetris?

The name “Tetris” comes from a combination of two words:
• “Tetra” (from Greek), meaning “four”, because every Tetris piece — called a tetromino — is made up of four squares.
• “Tennis”, which was the favorite sport of the game’s creator, Alexey Pajitnov, a Russian computer scientist.

So Pajitnov blended the two to form “Tetris” — literally meaning “four-tennis.”

He invented the game in 1984 while working at the Dorodnitsyn Computing Centre of the Soviet Academy of Sciences in Moscow. The simple geometric design and satisfying gameplay made it one of the most iconic video games in history.