Meaning- To cry or complain about an event that has already taken place and can’t be changed.
Usage- I’m sorry your wallet fell overboard, but there is no use crying over spilled milk.
Origin- First used in the mid 1600s and popularized by Canadian humorist Thomas Haliburton around 1836.
Note- sometimes you will see SPILLED spelled as SPILT . That’s because this is an old idiom and spilt is an old spelling.