Essulf FitzUlf, de Birkin

Have also seen him as Essulf Askvephus Enfulsuqui b. 1090.

Essulf had at least 8 sons who took their second name from their place of ownership and principal residence. In 1100 a law was passed, essentially to assist with taxation in England, that every person must have a second name. Here the toponymically derived names from the ownership of estates at Thornhill, Birkin and Tong are given for Essulf. The manor of Shelf, north-east of Halifax was granted to Essulf a predecessor of the Thornhill family of Thornhill. This grant occurred after the 2nd earl Warrene's [William Placetis, d. 1138] tenure of the manor of Wakefield who had previously been granted the manor of Shelf. In 1316 Shelf ('Shef') was held by 'Johannes de Schorell' who was probably John de Thornhill. [Nomina Villarum, 1867, p.361.]

http://midgleywebpages.com/thornhill.html