First the definition, almost correctly puzzled out by Mary and Rachel and Velma (with Lisa doing a good job of identifying the fewtrils themselves ): a fewtril is a trifling thing with little or no value.(OED Shorter)
But-- this morning I was noticing outdoor fewtrils as I clomped down the hill behind my house. I first saw a cow flop and thought that was surely a fewtril, but then I remembered collecting cow manure from this very field to put on my garden and also to make paper from. I picked up an empty black walnut husk, gooey and black and worthless to me; but then I remembered collecting these things to make walnut ink. The jimson weed pods were surely of no value, but in a way even they have worth as seed holders to continue that species. And so on. So I concluded that fewtrilhood is a relative state.