late 14c., Pigmei, "member of a fabulous race of dwarfs," described by Homer and Herodotus and said to inhabit Egypt or Ethiopia and India, from Latin Pygmaei (singular Pygmaeus), from Greek Pygmaioi, plural of Pygmaios "a Pygmy," noun use of adjective meaning "dwarfish."
It means etymologically "of the length of a pygmē; a pygmē tall," from pygmē "a cubit" (literally "a fist"), the measure of length from the elbow to the knuckle (equal to 18 "fingers," or about 13.5 inches; related to pyx "with clenched fist" and to Latin pugnus "fist" (from PIE root *peuk- "to prick"). The Greek use of the word in reference to the people presumably represents a folk etymology adaptation of a foreign word.
Figurative use for "person of small importance" is from 1590s. Believed in 17c. to refer to chimpanzees or orangutans, and occasionally the word was used in this sense. The ancient word was applied by Europeans to the equatorial African race, then newly discovered by them, from 1863, but the tribes probably were known to the ancients and likely were the original inspiration for the legend. As an adjective from 1590s. Related: Pygmean; Pygmaean.