I have recently came across half-adders and full adders in my Logic Network lectures. I have somewhat understood the theory, but I am still unable to understand the reason why they called them in that name? I mean, is there any reason why half-adders have the name ‘half-adders’?

With a full adder, you can get all outputs from (0,0) to (1,1). With a half adder, you can never get (1,1), which makes it, in a way, incomplete.

Also, in practice a full adder is used more than a bare half adder. For example, addition of binary numbers (one of the most common operations needed by a microprocessor) is done by chaining full adders:

I can't cite an historical reference, but I would suspect a "half adder" is called that because you can combine two of them (with an or gate combining the carries) to make a "full adder".