Term for words such as "un-f**king-believable" or "a-whole-nother" [duplicate]

Solution 1:

Tmesis is also used to describe this construction, when a lexical word is inserted as an intensifier. And yes, expletives are very often used as intensifiers in these cases.

It's also originally found in words like whatsoever/what-so-ever, howsoever/how-so-ever, etc., which are now words in their own right.

There are rules about where we stick the intensifier, based on prosody in English. We don't find *unbe-fucking-lievable but we do find abso-fucking-lutely. An interesting thing about a-whole-nother is where another is divided; it's not *an-whole-other as one would expect.

Solution 2:

Yes, it's called an infix. Its use in English is confined to such examples, but it is a normal feature of some other languages.