University of Michigan English Professor Anne Curzan has such a busy schedule, it's sometimes hard to find the time to produce our weekly "That's What They Say" discussion.

That led me to use the expression running from pillar to post, which in turn prompted a "hey, I wonder where that comes from" moment. 

We have lots of those moments, as do our listeners and readers, and that's why TWTS exists.

Where does the pillar to post reference originate?

"I'm afraid, as I sometimes do on this show, that I am delivering slightly disappointing news, which is we're not sure where pillar to post comes from," Curzan says.

But there are some theories.

"Some people use the expression to mean running around," Curzan says, "and some people use it to refer to movement, as in hither and thither, where you're not getting anything done. "There is a question of whether you're doing it of your own free will, or are you being forced from pillar to post. 

"It first shows up in the 15th century, and it shows up as post-to-pillar, and at some time got turned around."

One theory is the expression comes from tennis.

"The idea being here, that you tied the net between the pillar and the post, and if you were good at tennis, you had your opponent running, back and forth, between the pillar and the post," Curzan says.

But the timing doesn't quite work on this, Curzan says.

Another theory is that the expression may come from punishment.

"Criminals are moved from the post, where they're being whipped, to the pillory, or the stocks," Curzan says.

"Now as Michael Quinion, who has the great website World Wide Words points out, the problem is we have no evidence for the expression post to pillory. 

"Then there's the possibility that this is parallel to other expressions – like in Dutch, there's an expression van het kastje naar de muur, which means "from the cupboard to the wall."

The idea is that the cupboard and wall are not very far apart, so you're not getting much done.

As long as we're talking of pillars, where did pillar of salt come from?

"The pillar of salt, which is Lot's wife in the Bible, who turns to look at the destruction of Sodom and is turned into a pillar of salt. So that would be a more negative use of salt in the Bible, but with salt of the Earth, which comes from Matthew 5:12, that is a good thing," Curzan says.

You can also be worth your salt, which goes back to salt as a valuable commodity.

"Roman soldiers were paid their allowance to buy salt, and it's where the word salary comes from. It's the money you get to go buy things, and that's where the expression  worth one's salt – worth your salary – originates."

What if someone is described as salty?

"I love this expression," Curzan says. "Undergraduates are are using it a lot. I don't think it's a good thing if you're salty, but it's a great word."

It's not bad on margaritas, either.