1
general::
1. Fix or establish clearly, as in The firefighters finally were able to pin down the source of the odor. [Mid-1900s] 2. Force someone to give precise information or opinions, as in The reporter pinned down the governor on the issue of conservation measures. [c. 1700]
American Heritage Idioms
2
general::
Phrase(s): pin someone down (on something) [and] nail someone down (on something)
Fig. to demand and receive a firm answer from someone to some question. (Alludes to shifting from answer to answer; commit to one answer or another.) • I tried to pin him down on a time and place, but he was very evasive. • Don’t try to pin down the mayor on anything! • I want to nail her down on a meeting time., Phrase(s): pin something down [and] nail something down
1. Lit. to attach or affix something with nails or pins. • Pin the pattern down temporarily. • Nail down this piece of flooring every 12 inches. 2. Fig. to determine or fix something, such as a date, an agreement, an amount of money, a decision, etc. • It will be ready sometime next month. I can’t pin the date down just yet, however. • I can’t pin down the exact date just now.
McGrawhill's American Idioms And Phrasal Verbs