She knew I'd be interested in the infix in the middle of the word unbelievable, because I've posted previously about these additions within words.
Rachel Spack Koch, the moderator of Azar Grammar Exchange, after giving examples of infixes in English, concludes:
So, an infix is a letter, a syllable, or a word - sometimes invented - to put inside a word either to logically explain it, to add a a tone to it, or to encode it.To my ear, the headline would sound better as unbe-buddy-lievable, and I wondered why. I had a brief look at a paper discussing the way in which infixes are used in English and discovered the inserted word should lie to the left of a stressed syllable, and doesn't occur traditionally before a reduced vowel.
However, as it stands it does the job, celebrating Lance Franklin's thirteen goals this afternoon against North Melbourne.