Income is conventionally denoted by "Y" in economics. John Hicks made use of "I" for income, but Keynes wrote to him in 1937, "after trying both, I feel it is simpler to use Y for income And that i for financial commitment. Etymologists (folks who research the origin of phrases) https://emilianouiqfq.blogs-service.com/66125927/the-basic-principles-of-income-streams