What are "los sapwallas de Calcutta" ?
I found this expression in the book "La Vuelta al Mundo de un novelista por Vicente Blasco Ibáñez. He visited Calcutta, India in 1924 and wrote his experience in the book.
I think it is the name of a family "The Sapwallas", from Benares Sapwalla.
I may be wrong but I think that "sapwalla" was the local name for a snake charmer - un encantador de serpientes.
It means 'Snake Charmer'. This is very popular throughout India. Even now during festivals we can see them. They hypnotize the snakes by playing an instrument. This practice was there even during the mythological period.
"walla" or "wallah" roughly translates as "person/worker/person in charge of.." in India. A chaiwallah is the person who makes and sells the tea. "Chai =tea" So you have "rickshawwallah", etc etc. Given that, "sap" probably means "snake".