Recorded in many spelling forms including Allesbrook, Allsobrook, Olesbrooke, Holsebrook, Olsibrook, Alsebrook, Alsebrok, Alseybrook and Allsibrook, this is an English surname. It is almost certainly locational from a now 'lost' medieval village, since no place exists in the late 20th century in any of the recognised surname spellings. Locational surnames are by their nature 'from' names. That is to say surnames given to people after they left their original homes for whatever reason, and moved elsewhere. Spelling being at best erratic, and local dialects very thick, soon lead to the development of 'sounds like' forms. When perhaps because of plague or the loss of common grazing rights through the infamous Enclosure Acts, the village literally closed down, and the inhabitants dispersed, the loss of identity and the break up of the name became more pronounced. In this case the name is believed to derive from the ancient words 'alres' meaning river, and 'broc', which also means something similar of a brook or a stream. The name may be from Derbyshire area, but is well recorded in the city of London with examples including Jone Alseybrooke at St Giles Cripplegate in 1636, Mary Alseabrooke of Newgate in 1661, and Charles Allsebrook at St. Sepulchre church in 1751. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.