1748. T. Dyche, Dictionary (5 ed.). Barnacles (s.) ... in the
Canting Language, a pair of spectacles; also the irons or fetters
worn by felons are so called; also the gratuity or reward that
jockies have for buying horses for gentlemen.
Barndoor, subs. (sporting).—1. A facetious term for a target too large
to be missed; i.e., as large as a barndoor. Hence barndoor practice as
applied to organised battues, in which game is driven within a range
from which it is impossible to escape. This can hardly be called sport;
rather let it be known as ‘slaughter.’