Just a random thought, but why are iG and BLG called iG and BLG?

JDG (JD Gaming)
WBG (Weibo Gaming)
iG (Invictus Gaming)
BLG (Bilibili Gaming)
Among these, JDG and WBG are called JD and Weibo,
but Invictus and Bilibili are called iG and BLG.
What is the reason for this difference?
Just a random thought lol