Green’s Dictionary of Slang

an enormous unspecified amount.

1893		H.A. Bryden Gun and Camera in Southern Africa 184: Harking back to the loss of the Sultan, he exclaimed, ‘Na, na, it was nae accident, but just millions and drillions’ (he pronounced it ‘mullions and drullions’).
1948		Manone & Vandervoort Tempest 115: But, man, that record sold over a drillion copies [HDAS].
1971		Time 11 Jan. 24: Plus about a drillion dollars [HDAS].
1986		R. Davies Papers of Samuel Marchbanks 228: Today I heard a group of them boasting among themselves about how high they could count; such improbable figures as drillions and squillions were being bandied about.
1999		Guardian G2 19 July 9: Her house is worth drillions.
2002		Guardian G2 11 Feb. 9: Several drillion acres of forest have died to make the squillion copies of ever changing versions of national curriculum.