Calculus

Is there a mathematician in the house?
 
The word calculus has its origins in Greek khalix (small pebble) and Latin calx (small stone), perhaps from the ancient use of pebbles as reckoning counters.
 
Calculus, as the mathematical method of treating problems by the use of a system of algebraic notation, was developed by Isaac Newton in the 1660s. Calculus is a Latin word, originally meaning a reckoning or an account.
 
Since 1732, the word calculus has been used in medicine to mean kidney stones and, later, any concretion occurring accidentally in an animal body; e.g., dental plaque or calculous.  
 
Related words include a calculator (a mathematician) and a calculation, both from the late 14th century. The verb ‘to calculate’ meaning to estimate by mathematical means is from the 1560s; meaning to plan or devise is from the 1650s.
 
Reference: Online Etymological Dictionary, https://www.etymonline.com/
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