billionn.

Etymology: < French billion, purposely formed in 16th cent. to denote the second power of a million adj. and n. (by substituting bi- comb. form for the initial letters), trillion and quadrillion being similarly formed to denote its 3rd and 4th powers. The name appears not to have been adopted in English before the end of the 17th cent.: see quot. from Locke. Subsequently the application of the word was changed by French arithmeticians, figures being divided in numeration into groups of threes, instead of sixes, so that French billion, trillion, denoted not the second and third powers of a million, but a thousand millions and a thousand thousand millions. In the 19th century, the U.S. adopted the French convention, but Britain retained the original and etymological use (to which France reverted in 1948).Since 1951 the U.S. value, a thousand millions, has been increasingly used in Britain, especially in technical writing and, more recently, in journalism; but the older sense ‘a million millions’ is still common.