Hercules is the name of an Ancient Greek God. Do a search in google with Ancient Greek Gods + Hercules, and you will get a lot of information about him.
If it has been used as a descriptive word for a person ie - he's a Hercules, it means he is exhibiting the traits that Hercules is known for - namely strength.
Hercules is the most admired of all Greek idols. He was renowned for unusual power and bravery. Alcmene, wife of Amphitryon, made love to individually Zeus and her husband on the unchanged night and bore two sons, Hercules (son of Zeus) and Iphicles (son of Amphitryon). Hercules acquired the never-ending anger of Hera for the reason that he was the kid of her disloyal husband. Hardly any months following his birth Hera set two serpents in his support, but the exceptional baby swiftly strangled them.
Hercules is the Latin name which is used in Rome for the holiness parallel to the Greek mythological hero Heracles. He was son of Jupiter and tender grandson of Theseus, the Roman complement to the Greek god Zeus and the corporeal Alcmene. He was asked to play twelve great tasks, called The Twelve Labours of Hercules and became a god.
Hercules in plain english means: Hera's Rare Glory and Hera means soul so in plain english it means "The Glory of the Soul"