In grammar and rhetoric, the separation of the parts of a
compound word, now generally done for humorous effect
The art of breaking one word into two parts, inserting a different word (often an expletive) in between those two parts, hence forth turning two different words into one in order to give extra emphasis
from Greek, a cutting, from temnein, to cut (see tem- in Indo-European roots)
Examples of tmesis are found in the following, well-known quotes:
La-dee-freakin-da, a less offensive alternative, was made famous via Chris Farley on SNL.
Wel-diddly-elcome, one of many ri-goddamn-diculous phrases Ned Flanders often drops on the Simpsons.
Other famous phrases include:
Fan-fucking-tastic (The Departed)
Ala-fucking-bama (My Cousin Vinny)
Viet-fucking-nam! (Forrest Gump)
I'm not o-fucking-kay (My Chemical Romance)
That makes him a lia-fucking-bility (Boondock Saints), and
A whole 'nother' (insertion of "whole" into "another," rather than "a whole new")