‘I shall be obliged if you kindly let me know the meaning and origin of the word “BANKSHALL”‘.
Here is the entry for ‘bankshall’ in the Ibis Chrestomathy which can be found here.
‘+ bankshall: Neel would have been saddened by the demise of this beautiful word, once much in use: “How well I remember the great Bankshall of Calcutta, which served as the jetty for the disembarkation of ship’s passengers, and where we would go of an evening to gawk at all the griffins and new arrivals. It never occurred to us that this edifice ought to have been, by its oracular definition, merely a ‘warehouse’ or ‘shed’. Yet I do not doubt that Sir Henry is right to derive it from the Bengali ‘bãkashala’”. He would have been surprised to learn that a humbler kind of warehouse, the godown, would survive in general usage, at the expense of the now rare bankshall.’
But you might want to look at the entry in Hobson-Jobson. There are several editions available online; you will find one here.