Quantum
mid 16th century (in the general sense ‘quantity’): from Latin, neuter of quantus (see quantity). Sense 1 dates from the early 20th century.
wiktionary
From Late Latin quantum, noun use of neuter form of Latin quantus(“how much”).
etymonline
quantum (n.)
1610s, "sum, amount," from Latin quantum (plural quanta) "as much as, so much as; how much? how far? how great an extent?" neuter singular of correlative pronominal adjective quantus "as much" (see quantity).
The word was introduced in physics directly from Latin by Max Planck, 1900, on the notion of "minimum amount of a quantity which can exist;" reinforced by Einstein, 1905. Quantum theory is from 1912; quantum mechanics, 1922. The term quantum jump "abrupt transition from one stationary state to another" is recorded by 1954; quantum leap "sudden large advance" (1963), is often figurative.
