mid.

Abbreviation of Midland or Midlands. [The loosely-defined region of the United States that is between the North and the South, where Midland American English is spoken.]

Abbreviation of Middlesex. [A former inland county of England, partly absorbed into the erstwhile County of London in 1889; finally abolished in 1965 and absorbed mainly into Greater London, the south-west corner of the county becoming Spelthorne Borough and included in Surrey. The whole county, in whatever form, had the Thames as its southern boundary.]