Ameritrade bought the business from TD Waterhouse which was separated from the TD Bank 多倫多道明銀行 (Toronto Dominion Bank) in Canada, then rename the company's name to TD Ameritrade. Eventually Schwab bought TD Ameritrade in 2020.
In2020 there are a few of these kinds of brokerage houses acquisitions.
https://www.morganstanley.com/press-releases/morgan-stanley-closes-acquisition-of-e-trade
