Here are some idioms that might be similar in meaning and could be what you are thinking of:
* "As sure as eggs is eggs" - This is a more common version of the idiom, and it signifies something that is absolutely certain, like death and taxes. The repetition of "eggs" for emphasis reinforces the certainty.
* "Sure as shooting" - This idiom emphasizes absolute certainty, similar to "as sure as eggs is eggs."
It's important to note that the origins of these idioms are unclear and likely evolved over time.
If you can provide more context about where you heard this idiom, it may be easier to determine the correct phrase and its origin.