butitdon'tdonogood为什么译文译成“可是一点用也没有”.Mywifehasgivenherthings,youknow,likepeopledo,butitdon'tdonogood.Andthere'sbeenalotofsicknessaround.Sowetho'tyou'dbetterlookheroverandtelluswhat

Question

but it don't do no good为什么译文译成“可是一点用也没有”.
My wife has given her things,you know,like people do,but it don't do no good.And there's been a lot of sickness around.So we tho't you'd better look her over and tell us what is the matter.
这是自考00600高级英语上册第三课里头一句话.
但是我看着有点儿不懂.
译文：
我太太给她吃了一些药,你知道,大家都是这样做的,可这些药根本不管用,而且,附近有很多人都生了病,所以我们想请您最好给她检查一下,然后告诉我们是怎么一回事.
原句如上,请问
1.it don't do no good是什么句式,为什么译成“不管用”?
2.tho't=thought吗?

Answer 1

课文后面有一个解释,说it don't do no good是作者特意把有语法错误的句子写来表示说话的这位父亲受教育程度不高.The father uses a wrong form of the verb and double negative,by which the author indicates that he is not well educated.