First mentioned in Ivan Turgenev’s Fathers and Sons. The character who is a nihilist is a young man interested in science who does not support traditional social values. Best book on the subject is Nihilism by Stanley Rosen.
Essentially nihilism is when there are two things in conflict with each other, and you eventually realize that they are really the same thing. So it is the loss of the ability to make a distinction and thus a loss of meaning.
Nihilism is the fundamental product of the Western worldview, i.e. look around and you will find nihilism everywhere. Nihilism can be seen in Alienation and Anomie. Anomie is a term of Durkheim for loss of meaning. Nietzsche and then Heidegger talk about this aspect of the Western worldview. Heidegger says the essence of technology is not technological but is nihilism.
The primal scene of Nihilism in our tradition is when Achilles has his war prize Briseis, a female slave, taken from him by Agamemnon. Achilles sees that the Greeks are no better than the Trojans because the whole war the Greeks are fighting is for Helen who was taken from Menelaus by Paris. So Achilles withdraws from the fighting until Patroclus is killed.
Basically the epics are a working out of this quandary about how to deal with endemic nihilism within the Western worldview.
For instance, Odysseus is blamed for excesses that occurred when the Greeks took the city. This summoned up the wrath of Athena. Menelaus decides to flee and Agamemnon decides to stay on the beaches and sacrifice. The one who fled got home later, and the one who stayed got home sooner and was killed by his wife. Odysseus oscillated between the two, first going with Menelaus but then deciding to go back and join Achilles but missing the sacrifice. Because he was indecision, oscillating between the two nihilistic alternatives of fleeing and sacrifice to atone for the excesses Odysseus gets home last and after much struggle. Much of his struggle has to do with his encounters with images of nihilistic opposites.
So nihilism is very basic to the Western worldview. It has to do with the production of illusory opposites that conflict but are really the same thing extremes that lead ultimately to the same thing in the end.