Actually, that's not correct. Here's a re-post of info from 2014.
Neil Hurst explains, "
"During the early years of the hunting shirt, the garment remained highly regional, blocked from the east by the Blue Ridge Mountains
. Recorded in a will book from Augusta County at the death of one man named John Smith established the first written reference of the term hunting shirt in the eighteenth-century.
At the death of Smith in 1759 without a will or heirs, the county clerk recorded an inventory of Smith’s Located in the heart of the Shenandoah Valley of Virginia, Augusta County formed from Orange County in 1738 as Virginia’s largest county without a western border until the American Revolution.
The small inventory received an appraisal of twenty pounds, with his horse as the single most expensive item. Clothing constituted the majority of the recorded items and these garments included a jacket, coat, leather britches, leggings, shirts, and most importantly a hunting shirt.
So at least we know by 1759, the Hunting Shirt was well known enough that an Augusta County Clerk recorded it simply and with no explanation needed.