Doktor Avalanche
Please google 'STFU'.
So I did... Google it, I mean... And here are the results for STFU as an acronym:
Star Trek Federation University
Sir, That's Freakin' Ugly
Samurai Training Finished Unsuccessfully
Show Them Fury Unleashed
Say, Thanks for Understanding
Short-Term Follow-Up
Southern Tenant Farmers' Union
Special Task Force Unit
Super Time Force Ultra
Stop Trolling for Unicorns
Of course it can also mean, Shut the Freak Up, and/or, Scrawny Two-Faced Underling...
I suppose only the original poster knows his true intent?
My bet is on: Say, Thanks For Understanding