Well, sir, you'll be covered with cobwebs if you go into it. Why, it hasn't been opened for nearly five years, not since his lordship died.
请问:not since 是什么意思?
翻译:好吧先生,您要是进去的话会全身盖满蜘蛛网的。欸,它已经有近五年没打开过了,打老爷去世后就没开过。
这里的 not since his lordship died 是对前一句进行补充说明,not 其实是对前一句相似部分的省略。
补全省略的部分之后,其义自现:it hasn't been opened since his lordship died。