fork over

John GrishamのThe Racketeerを読んでいます。
Because it’s a rush job, Vanessa forks over $1,000 in cash, and they get down to business.
What they don't want is protracted litigation on many fronts, with verdicts landing everywhere. Neither do they want to fork over tens of millions for defense. “Phelps has plenty of money, Adam. In fact, I donate a lot of it to Auburn House. We have an annual fundraiser now at the Peabody, black tie and champagne, and I make Phelps lean on his banker buddies to show up with their wives and fork over the money. Raised over two hundred thousand last year.”
"fork over" なる慣用句は昔読んだイデオムのテキストブックに出ていて、フォークでお札を刺して渡している挿絵があったのを思い出しました。
この表現の由来が気になったのでEtymology Onlineで "fork" の項を見ると次の説明がありました。
early 14c., "to divide in branches, go separate ways," also "disagree, be inconsistent," from fork (n.). Transitive meaning "raise or pitch with a fork" is from 1812. Related: Forked; forking. The slang verb phrase fork (something) over is from 1839 (fork out) "give over" is from 1831). Forking (n.) in the forensic sense "disagreement among witnesses" is from c. 1400.
separate→disagreeで渋々払う連想はできます。ネットで更に調べると
super beefyなるサイト(http://superbeefy.com/where-did-the-expression-fork-it-over-come-from-and-what-does-the-phrase-hand-it-over-mean/)に次の説明がありました。
The expression “fork it over” has a connotation of urgency to it and is often used dramatically during a criminal holdup.
In fact, the expression does have origins in a long-forgotten underworld.
Of course, the phrase can also be employed with humor when asking for a financial payment for goods or services rendered or for the repayment of a loan.
The “fork” in question is a reference to “fingers,” which were the original dinner forks, especially for thieves and other low-lifes.
フォークは確かに手を連想できるので、"fork over" がお金を手渡しする意味があっても当然ですね。