Short answers, pulled from the story.
The taka, also called the tanka or tangka, was one of the major historical currencies of Asia, introduced in the 14th century and used along the Silk Road. It became especially prominent across the Indian subcontinent and Tibet, with Bengal serving as its historical stronghold.
The word taka comes from the Sanskrit ṭaṅka, meaning silver coin, according to The American Heritage Dictionary of the English Language and Banglapedia. It is linked to the Turkic təñkə, meaning coin or money, with related forms in Bashkir, Tatar, Uzbek, Kazakh and Russian.
The Bangladesh Bank officially introduced the Bangladeshi taka in 1972, replacing the Pakistani rupee at par after the end of the Bangladesh Liberation War. Bangladesh's Security Printing Corporation produces the currency, which carries the symbols ৳ and Tk.
Sultan Shams al-Din Iltutmish established the tanka as the currency of the Delhi Sultanate, drawing on both Muslim settler and native Indian elements. The silver tanka weighed one tola of 96 rattis, about 11.2 grams, and split into 48 billon jitals.
Lhasa Newar merchants from Nepal introduced the tangka to Tibet in the 16th century while trading Nepalese tanka along the Silk Road. The Tibetan government began minting its own tangka in the 18th century, with the first coin struck in 1763-64.
The taka served as the most important symbol of sovereignty for the Sultan of Bengal, whose Sultanate established at least 27 mints in provincial capitals. In 1338, the traveler Ibn Battuta observed that the silver taka, not the Islamic dinar, was the region's most popular currency.