pinhook v. to speculate in race horses. Etymological Note: This is a jargonized variation of pinhook defined by the Dictionary of American Regional English as “to act as a pinhooker,…a small-time speculator in farm products, esp. tobacco, esp. one who buys directly from farmers.” DARE traces the origins of later forms to the adjective pinhook, meaning “petty, small-time,” which is recorded as early as 1834 in Davy Crockett’s Narrative Life. (source: Double-Tongued Dictionary)
Scalper (scalping) is used in Iowa to describe actions similiar to “pinhooker (pinhooking).
The term “pinhooker” is rather commonly used (though not pejoratively)in Ireland particularly to identify certain professional horse buying agents.