meaning of xnor

xor means exclusive or, ie a OR b, excluding the case when both are true. but what about xnor, what is the meaning of the word exclusive here? why exclusive nor, instead of not- exclusive or nxor?

  XNOR Truth Table
  ----------------
  Input      Output
A    B
0    0    1
0    1    0
1    0    0
1    1    1

So, XNOR is ==. Why the hell do you need XNOR?