Minas Morgul meant Tower of Sorcery.

It was renamed from Minas Ithil in TA 2002 when it was captured by the Nazgûl. From then, it remained at war with Minas Tirith in the west.

The beautiful carvings of Minas Ithil were defaced into terrible beasts, and changed into signs of evil.

After the War of the Ring it was the duty of Faramir, Steward of Gondor to cleanse it of the horror that lurked there after its occupants were gone.
Encyclopedia entry originally written by Hathaldir