According to lore included in The Thigpen Tribe, the surname THIGPEN was first adopted in the late 11th Century.
Prior to the invasion of the UK by William the Conqueror, few people had surnames. They were largely identified by the chosen trade, a landmark near where they lived, a physical trait, etc. William required that all subjects adopt a family surname to facilitate taxation and census enumerations. The legend states that the THIGPEN ancestors were prosperous merchants whose original surname was THICKPENNY. Through the years, this name supposedly mutated to become THIGPEN in the New World.
The Thigpen Tribe is a tough resource to use. Smith's original intent — to compile all of the known research data related to the surname THIGPEN and identify its descendants — was laudable. The problem is that much of the research is undocumented. Combine that with fact that Smith lost much of her data in a fire in the late 1950's and had to piece her tome together from scribbled notes and the charity of others and one is left with a resource whose quality is sketchy at best.
Many less competent researchers practice the dubious technique of seeking only to trace their THIGPEN ancestry to this book, establish a connection to one or another line, graft that entire tree to their own, consider their research complete and begin propagating incorrect information. One can search this (Ancestry.com) and the GenForum message boards for this topic and find dozens of reports where the information available in The Thigpen Tribe bears little to no resemblance to reality.
YMMV, but this resource should be approached with a great deal of skepticism. Take its contents with a grain of salt and do your own research to verify or refute the data presented.