Resume work, usually with some reluctance, as in With my slavedriver of a boss, even on Saturdays it's back to the salt mines. This term alludes to the Russian practice of punishing prisoners by sending them to work in the salt mines of Siberia. Today the term is only used ironically. [Late 1800s] Also see keep one's nose to the grindstone.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.