I was drawn to the phrase “pass peach seeds” in Thomas Harris’s novel “The Silence of the Lambs,” which I started to read last month and from whose text I have posted several questions, including one relating to this passage:
“Don’t spill that (Coke mixed with Jack Daniel’s)” in here, “Jeff said. “Don’t worry, Jeff” Mapp said. Quietly to Starling, “You should have seen my man Jeff waiting for me outside the liquor store. He looked like he was passing peach seeds.” When Mapp saw the whisky start to work little, Mapp said, “How you doing, Starling?” -ibid.351.
Though I gather from the context that “pass peach seeds” means “avoid / duck out of an undesirable thing / matter”, I’m unable to find this phrase in the dictionaries I have at hand. Google Ngram doesn’t recognize this phrase either.
However, I found the following example of “pass peach seeds” in Yahoo Answers:
Will my dog pass this peach seed? - If it's whole - not likely. You really ought to keep an eye on your dog and see how she does. If she continues to eliminate and eat normally, she's going to be fine.
What is the exact meaning of “pass peach seeds”? Why should it be "peach seeds," not apple, pear or grape seeds? Is it a popular idiom, or just a one-off figurative expression used by the author? Would you show me another good example of employing this phrase?