Technology

Whale is a term that became popular with the rise of online games, specially on mobiles, that rely heavily on microtransactions for their income stream

The companies behind such games internally use the term whales for players/customers who spend ludicrously and disproportionately high amounts of money on the game. Often these players are addicted to the game or there are other psychological factors at play.

Most importantly, income from whales accounts for a large portion of the total income. There is this talk by a mobile game dev that went viral because he very casually talks about the exploitative nature of his games with no self awareness: https://youtube.com/watch?v=xNjI03CGkb4

Since then the term is used in other businesses where applicable. Here a small number of customers are accounting for about half the revenue so they are being called whales.