Though there is no dispute that songs may have nonsense lyrics, the song "Seven Nation Army" by the White Stripes actually have very coherent lyrics.
However, one line stands out as some type of idiom that I cannot decipher:
And if I catch it coming back my way I'm gonna serve it to you.
I infer that this is some type of threat, both by the "I'm gonna …" and also by the context of the rest of the lyrics. But what is "it", and what does "serve" mean? Perhaps "serve" is to "return the (it) back to you"?
Surely Jack White didn't just throw in a single nonsense sentence to an otherwise very coherent and well-focused work.
Best Answer
One of the meanings of serve is to give or present, such as "serve food". In this case the song is clearly not talking about food, however, serve has at least another 2 specific usages, which are also related to the action of giving or presenting. One is in a legal context, where serve means "formally deliver", usually documents such as a court summons. The second comes from tennis where to serve means to start play by hitting the ball towards the other side of the field. In both these cases the serve requires handling of some sort if repercussions are to be avoided (ignoring a summons could lead to trouble and not receiving a serve in racket sports results in losing points)
Whatever "it" is, he is going to give / throw it to you. The "back" is interesting here:
would mean that you are sending something his way and he would send it back, strongly implying that he doesn't want "it" from you (but then the lyrics wouldn't fit with the melody).
As it is written it seems to imply that he sent "it" to a third person (since it is coming back) and if "it" is sent back to him, he will pass "it" on to you.