Sentence:  “Well, Mars Tom, my idea is like dis. It ain't no use, we "can't" kill dem po' strangers dat ain't doin' us no harm, till we've had practice — I knows it perfectly well, Mars Tom — ‛deed I knows it perfectly well. But ef we takes a' ax or two, jist you en me en Huck, en slips acrost de river to-night arter de moon's gone down, en kills dat sick fam'ly dat's over on the <WSD>Sny</WSD>, en burns dey house down, en —” 
Meaning of the word marked with <WSD> tags:  A small channel of water.