1 adv. — Geography
further south; often the highly populated belt close to the Canada-US border.
Type: 3. Semantic Change — The general definition of down south in the OED-3 (s.v. "down" (31)) is simply "in or into the south". Consequently, the expression takes on very different meanings depending on the location of use. In the US, for example, it has long been used in reference to the southeastern and south-central states, with citations dating back to 1834 (see DAE, s.v. "down south"). In Canada, down south is often used to refer to the densely populated regions just above the border with the US (for examples of specific cities, see the 1977 and 1985 quotations). However, sometimes it is used by those from the far north to refer to areas like Muskoka (see the 1924 quotation) or the Peace River Country (see the 1954 quotations) that are south of where they come from, but north of the major cities. Muskoka is 200 km north of Toronto; the Peace River country is 500 km north of Edmonton.
See also: back east 49th parallel
2 adv. — Geography
in or into the United States.
Type: 3. Semantic Change — While down south in Canadian English can be used to refer to the highly populated belt just north of the Canada-US border (see meaning 1), it can also refer to the United States. Though usually not listed in Canadian desk dictionaries, there is significant Canadian evidence for this meaning, together with a long pedigree.