Why is the tongue the strongest muscle in the human body relative to its size?

In truth, the tongue is not the strongest muscle in the human body. But, one does need to look at the type of muscle (voluntary or involuntary), and which type of cells it is made from, plus what is its use.
The heart is the hardest working muscle in that it pumps blood throughout the entire body.
The tongue works constantly, not only when one is awake, but also during sleep, keeping saliva and obstacles flowing down the throat.
Other muscles, including the jaw muscles, which are powerful in that they control the actions of the mouth and throat.
Then there is the gluteus maximus, which one may laugh, but its job is not only for sitting, but it is responsible for holding the torso erect and helping one to walk up stairs.