One of the mysteries of the English language finally explained.
Any of the pins of a heckle. Compare hackle pin. Now historical.
to be on heckle pins
Informal and variants: to be in a state of anxiety or agitation because of uncertainty about a future event; to be on tenterhooks.
Mid 18th century. From heckle + pin.
heckle pin/ˈhɛkl pɪn/
In this article we explore how to impress employers with a spot-on CV.