Why could you argue that the word choice is correct when one “spilled the beans” about the “crying over spilt milk”? Well, in essence, it’s all a matter of the dates and locations of the two idioms’ origins. Let’s dive into “spilt” vs. “spilled.”
While “spilt” was the original past tense form of the verb “spill,” the most commonly used past tense form today is “spilled.” It’s this newer form I recommend to you for no reason other than it’s the one that has fallen into style.
As we know from discussions of “wend” vs. “went,” verb forms sometimes evolve. This “spilt” vs. “spilled” shift seems to have happened in American English first—in the early 1900s—and then afterward in British English, though the latter still gives occasional love to “spilt.”
Getting back to my original question, the expression “spilled the beans” was first noted in an American newspaper, The Stevens Point Journal, in a 1908 article discussing sneaky politicians. (Oh how times haven’t changed…)
“Crying over spilt milk” finds its first written usage in Jonathan Swift’s 1738 British publication Polite Conversation.
Thus, if you were to stay true to the era of these idiom’s origins, you would speak of “spilled beans” and “spilt milk.”
Yes, “spilled” is the better form to use in most instances these days, but you have to admit, a little burst of language nostalgia is sometimes fun. And this idiom is one of the few places you can still write “spilt” without raising too many American eyebrows.