leave (something) on the table
v. phr.— «He admitted he does have bad dreams occasionally about an estimator’s most dreaded mistake—“leaving something on the table”—in layman’s terms, forgetting to include a figure in a final estimate.» —“Construction-cost estimators can ruin builder with bad guess” Chicago Tribune June 24, 1973. (source: Double-Tongued Dictionary)
Further reading
Ian in Jacksonville, Florida, wonders about why musicians use the word clam to mean “a mistake” or “an egregious musical error,” as in There are a lot of clams in there or We need to practice where the clams are regarding a...
Quiz Guy John Chaneski has crafted a quiz involving a polysyllabic word followed by another word that repeats the last of those syllables twice. For example, suppose the clue is: “When playing a simple game with a toddler, it’s a real...