But as this gives something like one thousand quadrillionth part of the density of water, we refuse to accept or even think of it.
1670s, from French quadrillion (16c.) from quadri- "four" (see quadri-) + (m)illion. Cf. billion. In Great Britain, the fourth power of a million (1 followed by 24 zeroes); in the U.S., the fifth power of a thousand (1 followed by 15 zeroes).