Adam Clarke on Matthew 27:54

The centurion - The Roman officer who superintended the execution, called centurio, from centum, a hundred, because he had the command of one hundred men.

Truly this was the Son of God - An innocent, holy, and Divine person; and God thus shows his disapprobation of this bloody tragedy. It is not likely that this centurion had any knowledge of the expectation of the Jews relative to the Messiah, and did not use the words in this sense. A son of God, as the Romans used the term, would signify no more than a very eminent or Divine person; a hero.