Arnish Moore Undershirt & Frock Coat.

Thigh-length undershirt of brown wool, front opening closed by a single button on the collar, one of a collection of finds from a body discovered in a bog on Arnish Moor, Lewis: Scottish, early 18th century.

http://www.nms.ac.uk/explore/collection-search-results/?item_id=616058;

Thoughts on Wearing a Shirt.

It appears that some people think that the common shirt can be worn outside of the breeches. Now it has always been my understanding that the shirt was only worn out when wearing a breechclout. Further, it is my understanding that the undershirt was usually worn under other clothing, such as a waistcoat/weskit, jacket or  frock. There were acceptions of course, when men were working hard outside in summer they were known to remove outer clothing and work in shirt sleeves, but I have yet to see documentation that sais the shirt was deliberately pulled out of the breeches. The common shirt was in fact made very long, so that it could be tucked between the man's legs, & was in fact underwear.

This could be a shirt or a frock, depending on the weight of the material used. Frocks were generally made using a heavier material than was used for making an undershirt. This one appears to be buttoned at the neck, so it is more than likely a shirt and not a frock.

This claims to be a mid 18th century French undershirt, but it also claims to be made of a heavy flax linen. This is therefore in my opinion in fact a French froc/frock. Also note the linen ties at the neck. 

An 18th century bricklayer wearing a long sleeved weskit over a shirt.

A French peasant working in the fields. Note his undershirt is worn inside his breeches.

Again, no waistcoat for this peasant field worker, but his shirt is worn inside his breeches.

These two soap makers are wearing frocks.

This is a Dutch postman wearing a frock.

An Italian butcher wearing a frock.

A field worker in Brussels wearing a frock.

I think we can safely assume that these living historians interpreting French milice at Bedford Village are in fact either wearing breeches and frock, or they are wearing breechclout and shirt or frock.

Bedford Villiage- La Milice de la Belle Riviere 2009 

http://www.donegaltownshipriflemen.org/category/photo-gallery/milice-photos/

17th & 18th century underclothing for winter. An update on the under-waistcoat research.

17th and 18th century winter clothing for the common people.
Despite my earlier post on under-waistcoats, and undershirts, further research has found nothing to confirm that there ever was a specific undergarment. However, for those who are looking for more items of clothing to wear for winter, there is good news!
Although there is no proof of specific undergarments such as the under-waistcoat, an extra normal waistcoat can be worn under the normal shirt, or under another waistcoat. The same applies to an extra shirt, which can also be worn under another shirt. There is even documentation of two coats being worn at the same time.
Primary information for the above can be found at the following links: http://archaeologydataservice.ac.uk/catalogue/adsdata/PSAS_2002/pdf/vol_055/55_213_221.pdf
And http://ads.ahds.ac.uk/catalogue/adsdata/PSAS_2002/pdf/vol_106/106_172_182.pdf

18th century under-waistcoat & undershirt

Has resumed fires and wearing an under waistcoat. ...... Transcription of a letter from the King of Prussia to the Marquis d'Argens.

Marquis d'Argens wore the same flannel under-waistcoat for four years, for fear of catching cold.
Boswell (81).
“46 waistcoats, seventeen gilets” The Culture of Clothing.

WaistcoatsThere is some evidence for knitted men's undershirts (called waistcoats, but worn underneath the linen shirt) in the 17th and 18th centuries. The most famous example is the silk undershirt worn by Charles I to his execution in 1649.
Fashion in Detail by Avril Hart and Susan North, p. 184-5).

Woolen waistcoats were worn over the stays or corset and under the gown for warmth, as were petticoats quilted with wool batting, especially in the cold climates of Northern Europe and America. Fashion in the period 1750-1795. From Wikipedia, the free encyclopedia.

Camisoles or undervests are mentioned even less frequently, and it is not certain that they were always worn as undergarments. We have seen above that it was customary to wear a shirt directly against the skin, and it is known that the term "camisole" also can refer to a type of waistcoat (gilet). When made of flannel, as is the case with two camisoles in Duquesnel's inventory, [54] they were worn under a shirt. Besides two other camisoles, made of dimity (basin) listed in the same inventory, we do not know what other fabrics were used for camisoles.
Waistcoat: 1. Short sleeveless garment worn under a vest, jaquette ... etc. A sort of camisole of wool or cotton, which was worn next to the skin or over a shirt. The gilet is a vest without basques, and originally without pockets. (Larousse, XX siècle, "gilet").
CIVIL COSTUME AT LOUISBOURG: 1713 – 1758 MEN'S COSTUME BY MONIQUE LA GRENADE March 1972 (Fortress of Louisbourg Report H-F16AE) Translated By Christopher Moore (82)
Dispite the above quotes, I can find no evidence to date of a specific garment made to be worn under the normal shirt. The term undershirt seems to have come from the earlier period when jacket sleeves were slashed to show the shirt underneath.
A normal shirt, or waistcoat can be worn under another shirt, or two waistcoats can be worn together, one under the other. Older, worn shirts and waistcoats may have been used specifically for wearing under another shirt or another waistcoat where they would add extra warmth, but not be seen, as in the Arnish Moor and Barrock burial clothing.