hundred million, 10**8
億 centers on the vast number one hundred million (10^8), a concept used for counting extremely large quantities.
億 combines 亻 (person) with 意, which likely contributes the sound. The character was used to represent a large number, possibly from the idea of a person's thoughts (意) being countless.
A person (亻) trying to count to a hundred million would need immense thoughts (意). Imagine someone deep in thought, overwhelmed by the sheer size of 100,000,000.
For オク, picture an octopus with a hundred million tentacles: octopus -> オク, and the person (亻) is lost in thought (意) trying to count them all.
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hundred million; 100,000,000; 10^8
troublesome; bothersome; tiresome; annoying
apartment worth 100 million yen or more; luxury apartment
10,000,000,000; ten billion
100,000,000; one hundred million
national unity (esp. during wartime)
all-Japanese-are-middle-class mentality
national confession of Japanese war guilt (1945)
transformation of the population of Japan into idiots (because of television)
person who has a fortune of at least one hundred million yen; millionaire
millions and millions
billionaire; multimillionaire; very rich person
the people; multitude; masses
to show unwillingness (to do); to be reluctant (to do); to look annoyed; to show signs of finding something bothersome
eternity; paradise
1,000,000,000; billion
100,000,000,000; hundred billion
millions; vast fortune
several hundred million years