▲根据《牛津高阶英汉双解词典》：many’s the sb / sth who / that...是一个句式，意思是there are many people / things that...有很多的……人[事物]。如：

Many’s the promise that has been broken. 违反诺言的事经常有。

Many’s the time that I heard him use those words. 有很多次我听到他使用那些词语。

▲比较相关表达 many a … 的用法（两者意思基本相同）：

Many a promise has been broken. 违反诺言的事经常有。 

I heard him use those words many a time. 有很多次我听到他使用那些词语。