This rare surname is one of a group with the prefix "Middle". This was originally a pre 7th century Olde English word "myddel". which did mean what it said, in describing a "site" somewhere in the middle of somewhere else! In this case there must have been a place called Middlebrook, which was presumably a village, although it could have been a solitary farm, on an island in the centre of a brook. The old meaning of "brook" was a stretch of water, the translation as a running stream is much more recent. Some five thousand, or about 10%, of all modern British and Irish surnames derive from now "lost" medieval villages, of which the only reminder is the surname. There seems to be no reason why this should not be one of them. The (former) village of Middlebrook may have been in the West Riding of Yorkshire, as this appears to be the county where the name is most popular. The earliest recording been found in the Keighley area, although from the mid 17th century there was a branch in the village of Thorne near Doncaster. Early examples of surname recordings include Richard Middlebrook of Keighley on February 19th 1582, and George Middelbrooke who married Anne Whitacre, at Thorne on February 11th 1663. The earliest known church recording is probably that of Elizabeth Middlebrook, who was christened at Keighley on August 8th 1568, during the reign of Elizabeth 1st (1558 - 1603).