Trillion

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late 17th century: from French, from million, by substitution of the prefix tri- ‘three’ for the initial letters.

wiktionary

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From French trillion, from tri-(“three”) +‎ -illion.

Coined by Harvey Pollack, because of the way the numbers read across a basketball box score

etymonline

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trillion

1680s, from French trillion, from Italian trilione; see tri- + million. In the U.S., the fourth power of a thousand (one thousand billion, 1 followed by 12 zeroes); in Great Britain, the third power of a million (one million billion, 1 followed by 18 zeroes), which is the original sense. Compare billion.