Back to the grindstone.

Winter semester begins tomorrow.
I guess it's back to the grindstone.

xkcd sponsors TODAY'S MOMENT OF LEARNING, in the spirit of this.
I typed "back to the grindstone" into the Wikipedia search box, and this is what it gave me.
Ronnie Milsap discography
Apparently, "Back to the Grindstone" is the American country singer's 21st album, dropped in 1991 with the hit song "Since I Don't Have You." Good on ya, Ronnie. I might look you up if country happened to be my cup of tea.
Oconaluftee (Great Smoky Mountains)
This is the name of a river valley in North Carolina's Great Smoky Mountains that houses the main entrance to the nearby national park. Historically, Cherokee Indians have considered the river's water sacred, but it is apparently invisible to white people because they are blinded by evil. Huh. The flour mill there, Mingus Mill, uses grindstones to crush wheat into flour.
Ancient Egyptian Cuisine
Egyptians ground "emmer" wheat (more fascinated clicking-->a low-yielding wheat domesticated in the Far East) to make flour. Apparently, this type of wheat is very spiky, so the bread-making process was time-consuming; the wheat had to be painstakingly moistened and dried before the chaff could be effectively separated out.
A Tale of Two Cities
Just looking at the cover of Charles Dickens' literary masterpiece brings pleasant flashbacks of my twelfth grade class presentation on Lucie Manette. Wikipedia tells us that the grindstone reference here sends us to the part when mob-mad men and women massacre eleven hundred detainees in one night and hustle back to sharpen their weapons on the grindstone, displaying "eyes which any unbrutalised beholder would have given twenty years of life to petrify with a well-directed gun."

Maybe returning to the grindstone won't be all that bad. I'll use the knife I bought off a Parisian revolutionary to cut a few stalks of emmer wheat, humming Ronnie Milsap as I make my way to a river I won't be able to see.