Jerome : (Verse 18) And Jacob came to the city of Shechem, which is in the land of Canaan, when he came from Mesopotamia of Syria. A confusion arises, as to how Shechem is called the city of Salem, when Jerusalem, where Melchizedek reigned, was previously called Salem. Therefore, it seems that both cities have the same name, which we can also find for various places in Judea: that the same name of the city and place is in different tribes; or certainly we can say that the Shechem which is now called Sichem, translates to "consummated" or "perfect" in our language, and that the one which was later called Jerusalem is transferred to "peaceful". For both meanings of the word, with a slight difference in accent, this word is used. The Hebrews say that it refers to the limp of Jacob's thigh, where he became weakened and was healed. Therefore, they consider this city the same as the one that received the name of the cured and perfected. — Hebrew Questions on Genesis