Indic languages of the Indo-European (IE) family have the innate ability to usurp foreign words and Sanskritise them (tatsama) or make them sound like Saṃskṛta (tadbhava) — often with little or no change in morphology, except when translated sometimes — usually seamlessly. Bengali is still doing it without much furore: aňtňat আঁতাঁত (no change in morphology except the script) for entente, prātarāsh প্রাতরাশ (translated around Vidyasagar’s time) for breakfast, vaidyutin বৈদ্যুতিন (coined from vaidyutik বৈদ্যুতিক, a Saṃskṛta calque of electrical) for electronic. How many Bongs would suspect that siṃhabhāga (সিংহভাগ) is actually a calque of lion’s share? The word bastard was bastardised in French Chandannagar as betār (via bâtard); the latter literally means wire- (tār-) less (be) — radio, to be precise. My childhood friends from Chandannagar mouthed the abuse rather too fluently, blissfully unaware that be was a Farsi (Persian) prefix abundant in Bengal and the Bengali calque betār বেতার for radio was not older than No. 1, Garstin Place. I grew up ignorant of the true nature of the word which was usually uttered with another that literally meant bastard: betār-bejammā বেতার-বেজম্মা had a lilt to it, was the right mouthful to utter, and was far more mysterious than the arcane glossary of human organs and bodily acts that we were learning in school outside the official curricula.
Some were known to have been usurped by the hoary IE-speaking nomads from Central Asia who had entered Iran and India around (or before) 1500 BCE. Ushţra উষ্ট্র for camel is believed to have entered the IE lexicon — both Vedic and Avestic — during the passage. It has also been speculated that the Avestic name of Zoroaster, Jarathushtra, actually means ‘old (wise?) camel’. Tanḍula and dhānya for rice entered the IE lexicon much later, in the subcontinent for sure, from the Gangā-Yamunā doāb, perhaps. And rice, in turn, entered the English dictionary from Tamil. Tāmbul (betel leaf) is without doubt a word of pan-Mundari origin; it is better known as pān today — from Saṃskṛta parņa (leaf). Yet, the IE languages then and now were poles apart, Dravidian being an agglutinative language like some of the older tongues of the Mediterranean region.
The etymology of quite a few apparently Saṃskṛta words is not very clear.
I am almost certain, based on my personal search, that the verbal abuse śālā, spelt with a palatal ś but pronounced dentally in Hindi and its kindred tongues, and as sh (শ) in polite Bengali, is not derived from Saṃskṛta śyālaka, though it has come to connote “I-sleep-with-your-sister” at a much later date. Had it been otherwise, we would have seen it in at least one of the many pre-Islamic Saṃskṛta and Prākṛta plays (openly ribald) and lexicons. It is, I believe, in unmeaning imitation of the last two syllables of Insh’allah, picked up from sufi dervishes, foreign traders and conquerors, and initially used as one of many interjections. I await the messiah who will research and confirm my suspicion.
Thākur, often Saṃskṛtised to thakkar, is believed by some to be a Turkic honorific. The argument that it must be Saṃskṛta for it is found in one of the songs of Caryāpada, does not hold much water; some of those songs were indeed written after the advent of Islam (initially Turkish, squarely a Turkic tongue; for many centuries the Bengali word for Muslims was Turki তুর্কী). That it has come to be a synonym of deity in Bengali (e.g. Durgā thākur দুগ্গা ঠাকুর) shows the innate obsequiousness of ethnic Bongs, perhaps.