'Executioner' in the Bible

Meanwhile, in Egypt the Midianites sold Joseph [as a slave] to Potiphar, an officer of Pharaoh and the captain of the [royal] guard.

Now Joseph had been taken down to Egypt; and Potiphar, an Egyptian officer of Pharaoh, the captain of the [royal] guard, bought him from the Ishmaelites, who had taken him down there.

Now there was with us [in the prison] a young man, a Hebrew, servant to the captain of the guard; and we told him, and he interpreted our dreams for us, to each man according to the significance of his own dream.