Dictionary definition of Gazillion: A very large (but indefinite) number or quantity (of something): chiefly in plural.
The first mention of this colloquial in British newspapers seems to have been in the Chronicle & Echo, 19 November 1991:
The next year, this message of celebration appeared in another newspaper on the 2nd of April [names have been redacted for this post]:
Artificial Intelligence on the ‘origins’ of Gazillion:
The word seems to have arisen in the United States of America. It is not clear when it ‘arrived’ in the United Kingdom.
