“Calculate” comes from Latin calculare, itself from calculus meaning “small stone” or “pebble.” Romans used pebbles on counting boards to perform arithmetic, and the act of moving stones became the word for computation. The same Latin word gave mathematicians the term “calculus” (Newton’s system of infinitesimal calculation) and geologists “calcium” (from calx, limestone — the parent of calculus).
“Disaster” comes from the Italian disastro — a compound of dis- (bad, against) and astro (star, from Latin astrum). Literally, a “bad star” — reflecting the Renaissance belief that the positions of stars governed human fate. An unfavorable stellar alignment was a disaster: celestial catastrophe written in the sky before it happened on earth.
“Muscle” comes from Latin musculus, meaning “little mouse.” Roman anatomists observed that a flexing muscle beneath the skin looks like a small mouse running — the bicep rippling under the arm resembles a mouse’s back moving. The same Latin word musculus also gave us “mussel,” because the shellfish’s dark, curved shape resembles a mouse.
The word “disaster” comes from the Italian disastro, which literally means “bad star.” It combines the prefix dis- (bad, against) with astro (star), from Greek aster. In the age of astrology, a disaster was an event caused by an unfavorable position of the stars — a calamity written in the heavens.