The word is derived from the Greek "atomos," meaning indivisible. The name was given to a tiny quantity in the field of physics, because it was wrongly thought that the atom was so small that it could not be split into even smaller units. Scientists have now discovered and released the great power obtained by splitting atoms.
WHY WE SAY...
A Guidebook to Current Idioms and Expressions — and Where They Came From
By Robert L. Morgan, Illustrated by Peter Hoffman
Sterling Publishing Co., Inc., New York, 1953.
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