barleycorn

n. [ See Corn. ] 1. A grain or “corn” of barley. [ 1913 Webster ]

2. Formerly , a measure of length, equal to the average length of a grain of barley; the third part of an inch. [ 1913 Webster ]

John Barleycorn, a humorous personification of barley as the source of malt liquor or whisky. [ 1913 Webster ]