# What is the most reliable way to find a particular function?

I learned there're built-in functions which is not documented　from this question.

After this ,
I tried looking for something which is usable for me,
then noticed that with ? something*,
I can't find the packages like Optimization without specifying ?Optimization'*.

Is there any way to search all-builtin functions with arbitrary phrase?

Names["**" <> pattern <> "*"]

?**pattern*

should find symbols containing pattern.