What is the earlier name of Mirkwood in J.R.R. Tolkien’s legendarium?

Mirkwood was earlier called Greenwood the Great in J.R.R. Tolkien’s legendarium.

Greenwood the Great was originally a vast forest in the northeastern part of Middle-earth. After the rise of the Necromancer, Sauron, at Dol Guldur, a growing shadow affected the woodland. It became known as Mirkwood, a name reflecting its darker and more dangerous character.

The forest is important in both The Hobbit and The Lord of the Rings. Bilbo and the dwarves cross it during their journey to Erebor, while later events involve the Elvenking Thranduil and his woodland realm. Giant spiders and other hazards make the passage especially perilous.

Mirkwood should not be confused with Fangorn Forest, which lies farther west and is associated with the Ents. Tolkien also used the name Mirkwood in relation to older Germanic and Norse traditions, but his forest has its own history and geography within Middle-earth.