There are words being used in this novel which are new to our language "scabland" "bloodcults" are some examples. What do these terms mean? Why is McCarthy combining words in this way?

I think McCarthy uses mixed words to provide a sense of otherness between this post apocalyptic world and our own world. The world the man and boy must inhabit is has become a barren wasteland where humanity is dead: It deserves its own horrid lexicon to describe it. Consider a few of these words below:

1) Slut-lamp- This speaks for itself, this would be a lamp-post where prostitutes stand in order to ply their wares.

2) Scabland- a rough, barren land

3) Bloodcults- cannibals