When written in all capital letters (OFF), this is an acronym for Our Favorite Family, aka The Simpsons. It is often used by fans in alt.tv.simpsons or in the episode capsules at snpp.com. This is not obvious to anyone who left the USEnet alt.* hierarchy a long time ago, but the die-hard fans still use it constantly.
The most obvious reason behind the emergence of the "OFF" acronym: both the show's title and central characters bear the same name. Consider the sentence:
Tonight on The Simpsons, the Simpsons help Apu get his job back at the Kwik-E-Mart.
Tonight on The Simpsons, OFF helps Apu get his job back at the Kwik-E-Mart.
See that? By using the acronym as a collective noun, we save eight bytes. You can save even more by using abbreviations like SLH for Santa's Little Helper, and so forth. In the end, you can shave milliseconds off the download time for an episode capsule, a boon for anyone downloading it over a 2400 bps satellite phone connection.