Definition of "diff"

[Pogo:] A woman outthunk is a woman scorned and you know what's got no fury like that! [...] Mus' I tell you? It's Sunday. [Albert:] What's the diff? Tell away. [Pogo, whispering:] Hell.

1960 March 13, Walt Kelly, Pogo, Sunday, comic strip, page 277

I didn't want to waste people's time telling them things they already knew. It's more efficient just to give them the diffs.

2004, Paul Graham, Great Hackers, Essay

Many operators cursed the early diff and driveline set-ups[.]

2000, Bob Foster, Birdum or Bust!, Henley Beach, SA: Seaview Press, page 45

Hemoccult emesis and stool, CBC with diff, PT/PTT, type and cross for PRBCs.

2006, “Gastroenterology: Esophageal Varices”, in Steven E. Diaz, The Little Black Book of Emergency Medicine (Jones and Bartlett's Little Black Book Series), 2nd edition, Sudbury, MA: Jones and Bartlett Publishers, page 103

As we move through this chapter, you will quickly see the benefits of diffing code changes to drivers, libraries, and applications.

2011, Gray Hat Hacking : The Ethical Hacker's Handbook‎, 3rd edition, New York: McGraw-Hill, page 484

I don't think it's any diff then in grade school when someone said "come on take a drag it will make you look cool"

2000 August 15, ZedMan2K, “Anti-Leiberman Backlash Already”, in alt.religion.christian.baptist‎ (Usenet)

Is there a way to tell it to pick a diff one by default?

2006 August 25, jes.t.er, “Character names”, in alt.games.warcraft‎ (Usenet)