Personal names can be used as a trademark only if it can be demonstrated that they possess "secondary meaning." Thus, personal names are similar to descriptive marks and they are considered to be weak marks. For the purposes of trademark registration, secondary meaning may be assumed after five years of continued and exclusive use of a mark. Black's Law Dictionary (Fifth Edition) defines the doctrine of secondary meaning for the purpose of trademark law as "[A] ... party through advertising or massive exposure ... [establishing] its trademark in the minds of consumers as an indication of origin from one particular source."

There are numerous examples of trademarks that use personal names: Chanel, Levis, Versace, Gucci, etc. These personal names are protected by trademark law because they have accomplished the objective of forming an association in the mind of the consumer which links the individual products with its manufacturer or distributor.

Reference:
[1] Stim, R. "Intellectual Property. Patents, Trademarks, and Copyrights" West Legal Studies.
[2] Black's Law Dictionary 5th ed., (West Publishing, 1979).