quintuplet (n.)

"fivefold, containing five times the number or amount," 1560s, from French quintuple (15c.), from Late Latin quintuplex, from Latin quintus "fifth" (related to quinque "five;" from PIE root *penkwe- "five") on model of quadruple. Alternative quintuplicate is attested from 1670s. Musical quintuple time has five beats to the measure.

1650s, "three successive lines of poetry," from triple; perhaps patterned on couplet. Extended to a set of three of anything by 1733, and to three children at the same birth by 1787 (another word for this was trin, 1831, on the model of twin). Musical meaning "three notes played in the time of two" is from 1801.

1935, originally in reference to the Dionne babies, short for quintuplet "one of five" (children born at one birth).