Kalidar was the name Blizzard gave the island off northwest Kalimidor, where Teldrassil was originally grown. The night elves moved their capital to the island. The Circle of the Ancients and the wise druids pooled their power to create a great tree akin to the World Tree, but on a smaller scale. The tree outgrew the island. , and the night elves built their city of Darnassus atop it. The island now takes the name of the tree as well, and a twilit forest now covers it. ( )
|"Off Kalimdor's northern coast lies the island of Kalidar, the new home of the reclusive Night Elves and a stunning testament to the power of their magic and their connection with nature. After the cataclysmic events that followed the invasion of the Burning Legion, the Circle of Ancients and powerful druids combined their powers to grow an immense new world tree on Kalidar. They called the tree Teldrassil, meaning "crown of the earth" in their native tongue. The night elves made their new home in the boughs of Teldrassil, creating a forest of mighty trees and flowing rivers, bathed in the endless night that fell over the lands of the elves from the dawn of time. However, the calm of the enchanted forest has slowly fallen into the shadow of a sinister presence. Crazed furbolgs and fouler beasts have appeared in Kalidar, and it occupies all the attention of the vigilant Sentinels and the wise druids to ensure the safety of their new home.
A sprawling city of moonstone and wood, the night elf capital of Darnassus stands as a shining beacon atop Kalidar. Within its mighty walls are housed countless druids, hunters, and warriors, led by the priestess of Elune, Tyrande Whisperwind. A stunning marvel to the ability of night elven craftsmen, the ethereal Temple of the Moon rises above the tree line, balanced by the druids' meticulously cultivated meditative grove. Trade from the main continent bustles through the city's trade quarter, where night elves, dwarves and humans alike haggle for wares and services. Delicate bridges and pathways crisscross the serene waterways of the city, the pristine waters reflecting the glowing light from the moons above."
In World of Warcraft
Kalidar was removed from early Alpha, it can be found in the gamefiles and it appears to have been intended as a battleground. Apparently, it has a Orcish and Human base opposite to each other. 
It is possible that the backstory of the island originally being called "Kalidor" was retconned out of lore. According to the Warcraft RPG, the original name of the island was never mentioned. However, it is confirmed that the island later became known as Teldrassil, named after the Great Tree that grew on it.