Because he's using the name of the Demon that asked for childrens to burn in the fire.
https://en.wikipedia.org/wiki/Moloch

Best regards.

Tophet is Moloch, which was made of brass; and they heated him from his lower parts; and his hands being stretched out, and made hot, they put the child between his hands, and it was burnt; when it vehemently cried out; but the priests beat a drum, that the father might not hear the voice of his son, and his heart might not be moved.

the flames of which engulf the child. When the flames fall upon the body, the limbs contract and the open mouth seems almost to be laughing until the contracted body slips quietly into the brazier. Thus it is that the 'grin' is known as 'sardonic laughter,' since they die laughing.