ἰσχυρὸς [3 verses](adj sg masc nom) "A strong man" is  ischyros, which means "strong", "mighty," and "powerful." It is from ischys, meaning strength. Here is seems as though it is used to refer to demons that control people. - -"A strong man's" is an adjective used as a noun. It means "strong", "mighty," and "violent." So it means "a strong one" or "the violent one."