This title's not too tricky to suss out.
The borrowers are the main characters in The Borrowers, so our title gives us a heads up on whom to root for. Duh.
But beyond that, it also points to a key question in the novel. What exactly is borrowing? Is it all that different from stealing? And if so, how so?
For example, if you borrow your big sister's skirt, but keep forgetting to give it back, is that still borrowing? Or something a bit more like stealing? Where do you draw the line?
If the folks we root for are borrowers, that should give us a hint that maybe borrowing isn't so bad. Just imagine if the book were called The Robbers. And hey, the boy seems a-okay with the whole borrowing thing. So maybe it all depends on how you look at it.