talk shop - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Converse about one's business or profession, as in Whenever John and his dad get together, they talk shop. [Mid-1800s]