administrative division of SE Scotland: formerly a county & district
See Midlothian in American Heritage Dictionary 4
(mĭd-lōˈthē-ən)
A region of southeast Scotland on the Firth of Forth surrounding Edinburgh. “The Heart of Midlothian” was a popular name for the former Tolbooth Prison in Edinburgh and was used by Sir Walter Scott as the title of his 1818 novel.