By switching the first letters of "damn" and "family", you can say the whole, entire, freakin' family is coming without actually cussing.
Usually spoken in redneck and/or back-woods families, where the family can be less than desirable to be around.
Dude ... is your ENTIRE family coming to the wedding?
Yes. My whole famn damily is coming. It's going to be so embarrassing.
A combination of the words "family" and "damn," placed in such a way so that friends and acquaintances who have heard you refer to yours can mistakenly mix the syllables and call them your "damn family".
"So my fandamily is coming in for the holidays. Aunt Ruth probably hasn't shaved her beard in a while."