Numericon gives the history of the words googol and googolplex:

… the famous

googol, 10^{100}(a 1 followed by 100 zeros), defined in 1929 by American mathematician Edward Kasner and named by his nine-year-old nephew, Milton Sirotta. Milton went even further and came up with thegoogolplex, now defined as 10^{googol}but initially defined by Milton as a 1, followed by writing zeros until you get tired.

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