Which caste does Verma belongs to?

Verma (Hindi: वर्मा) surname originally belongs to the Kshatriyas. The meaning of this word is "shield" or "protection" and it was a surname for warriors.
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References:
1. Dasa, Syamasundara (1965-1975). Hindi sabdasagara. Nagari Pracarini Sabha.
2. Dictionary of American Family Names, Oxford University Press, ISBN 0-19-508137-4.