Pure speculation, but could it be that the first syllable comes from the Tamil word kacu, which in turn refers to the Chinese word Tsien (cash in English, kas in Dutch)? Begh is a local honorific or part of a name. The whole would then be either "a cash coin of the Begh" (alternatively, a cash coin of a fellow who has Begh in his name) or "an honourable cash coin". It may look surprising that the word cash/kas travelled so far, but Asian denominations like denga (tanka) made it to Russia and so did cash. In Russian, it was deformed to chokh.
Peter