Raviji has explained the basis of common surnames in various castes.
We have tried to explain this subject in an article on JL Wiki. Members may read it here:
http://www.jatland.com/home/Jat_Clan_System
Panini has defined gotra in his grammar astadhyayi in sanskrit as under-
उपत्यं प्रौत्रं प्रभृति गोत्रम upatyam prautram prabhriti gotram
Translation – Gotra is the name of group of descents, leaving son, including grandsons and great grandsons.
Jat people Gotras have initially been created in the name of a person, a place or some historical incidence. When in a generation a great person takes birth all the previous titles of this generation are included in the name of this great person and a new gotra starts in his name. Like caste does not change, gotras and vanshas also do not change. There can be more than one gotra in a vansha but there can not be more than one vansha in a gotra. For example Chauhan vansha has 116 gotras included in it.
A clan gains political ascendancy, and other clans who support the ascendant clan, become part of a political confederacy. It was in this sense that the confederacies of Mor, Sakan, Kasuan, Oujar, Parmar, Chauhan, Rathors, etc. were formed. This does not mean that the members of the particular confederacy headed by a particular clan, were descendants or branches of the later ascendant clan. Therefore, in effect, the presence of a gotra in two castes only shows that the particular Jat clans, among others, were supporters of the Tomar or Chauhan, or Bhatti or Parmar or Gujar royal families when these later formed their kingdoms. It is on account of this factor that a particular clan is seen as part of more than one ascendant clan and
"the double ancestry". (See -
http://www.jatland.com/home/Jats_the_Ancient_Rulers_(A_clan_study)/Appendices/Appendix_I)
We have categorized Gotras on following basis
* Based on system of worship
* Nagavanshi Jat clans - These are based on animals, trees, birds, kings etc.
* Based on persons
* Based on places or natural features
* Based on languages
* Based on titles
* Based on professions
If a gotra was started by a person and this gotra is found in different castes it is very likely that they had a common epi-person. Branching of the family trees takes place over a period due to various reasons.
Regards,