Origin of the hand signals

What's the origin of the hand signals used in baseball today?

In the early 1900s, the New York Giants baseball team had a
pitcher named Luther H. Taylor. He was a deaf mute who was, in
an era of insensitivity, nicknamed "Dummy." Taylor lost a lot
of games due to his inability to communicate with his teammates.

John McGraw, the manager of the Giants, was under enormous
pressure from the team's owner, the fans and the sportswriters
to trade Taylor. Instead, McGraw (who seems to have been a Giant
of a man) required the entire Giant team to learn American Sign
Language. Once that was accomplished, McGraw used hand signals
to lead his team.

That's the origin of the hand signals that are used in baseball
today.