By night I went out through the Valley Gate toward the Jackal Well and the Dung Gate, examining the walls of Jerusalem, which had been broken down, and its gates, which had been destroyed by fire. Then I moved on toward the Fountain Gate and the King’s Pool, but there was not enough room for my mount to get through…Nehemiah 2:13-14

Over time the many gates around the city received names to indicate which one they were.  One probably led to a valley.  Another had a fountain.  The other could have been where animals were escorted in and out and did their business (dung).  We may call gates by their direction (east, west) or by the significance they played in history.