n. — Newfoundland & Quebec, Housing
an open, roofed area along the front and sometimes the sides of a house; a porch or veranda.
Type: 5. Frequency — In Newfoundland and Quebec, gallery refers not only to a building dedicated to art exhibitions, but to an elevated structure along the side of a house, chiefly called a "porch" or "veranda" elsewhere (COD-2, s.v. "gallery" (5)).
Boberg (2012: 497) lists gallery as one of many Gallicisms in Quebec, i.e. lexical and grammatical transfers from French. While Gallicisms sometimes arise out of need to comply with local signage dictated by Quebec's language laws, Boberg notes that the source of gallery in Quebec English is unclear and is likely a result of mere "contact between the two speech communities". The term has similarly gained salience in the US in the Gulf States, Arizona and Texas due to the influence of Louisana French (DARE, s.v. "gallery").
The origin of gallery in Newfoundland and Labrador English is less clear, as French populations on the island have been largely restricted to Acadians settling along the southern west coast in the early 19th century (Clarke 2010b: 113). However, gallery has been a part of nautical vocabulary for hundreds of years, with attestations in OED-3 dating back to 1627 (OED-3, s.v. "gallery" (2d)). Defined as 'a balcony built outside the body of a ship, at the stern, or at the quarters', it is likely that this maritime term was generalized in Newfoundland English to refer to similar structures on land (Clarke 2010b: 118).
See also COD-2, s.v. "gallery" (5), which is marked "N Amer (esp. Que., Nfld, & Gulf States)", DNE, s.v. "gallery".