Here’s a puzzle: why can’t you say “abso-jesus-lutely”? (Recently brought to my attention by Leland Paul Kusmer.)
Let’s back up for a sec. The classic case of expletive infixation involves “fucking” or “bloody” as in abso-fucking-lutely, abso-bloody-lutely. And one syllable swears can’t infix: there’s no abso-fuck-lutely or abso-shit-lutely. But “Jesus” is two syllables, people swear with it, and it even has the same stress as the other two. Why doesn’t it sound right as an infix?