To answer this, you need to dig down to the Indo-Persian root of the game, which is steeped in military strategy and ancient conquest.
The word checkmate is derived from the Farsi or Arabic شاه مات‎ or shāh māt, which means 'the King is helpless'.
The “māt”, which we recognize as “mate” means measured or traversed, alluding to the prowess of the opponent in taking the dominion in the game.
An alternate theory relates the term “mate” to the Arabic word “māta” meaning died or dead; not only that but staring, mouth agape, and stupified!