I caught myself saying this yesterday.

Problem:
“Inoften” is a made-up adverb.

Explanation:
I was tired yesterday when, seemingly out of nowhere, I said “inoften” instead of “infrequently” or something else.

This made-up adverb puzzled me because I did not recognize it, so I asked my wife. She said that she had never heard of it.

The word then amused me because it made sense. In other words, if a non-native English speaker said this, you probably would understand what he or she meant.

I looked up “inoften” in an online dictionary and got back “Did you mean unoften?” instead of a definition.

It turns out that “unoften” is in at least one dictionary as an obsolete adverb that mean not often.

A Google search for “inoften” returned about 671 matches — relatively rare for the World-Wide Web today. In contrast, Google found the obsolete adverb “unoften” about 32,600 matches — not so rare.

Solution:
“Not often”