some guy with a big stick 200 thousand years ago

I hate to be pedantic (I don't really) but your question is slightly wrong. It's a bit like saying who invented Murder. Its not that someone is respsonsible for creating the concept of terrorism, its more that we need to define it and understand the factors that lead to people to behave in this way. Religion and political reasons would be top of my list

Motorcycle racing began the minute the second motorcycle was built.

The Catholic Inquisition is interesting ... read "God's Jury" by Murphy. Or Google "Catholic Torture" and prepare to be disgusted.

Terrorism in various forms is as old as humanity. So is torture. It's a sad part of the human psyche too often. Peace.

Christians and other religions of the same type they terriffy you as children and train you to terriffy others call them terrorist

If you want to limit your inquiry to only the terror coming out of the Islamic world ... not sure when it started and by who. But have a fair idea who is feeding it. The extreme form of Islam practiced in Saudi Arabia has been systematically exported to other Islamic nations, very much to the detriment of these nations. The Saudis have been funding Mullahs to go all over the planet, ( a bit like I've met godforsaken fundamentalist "Christians" doing missionary stuff in the middle of the Pacific in the Cook Islands) , well, back to my point: there has been a very systematic undermining of liberal Islam, to the point that many people are dead, and many nations in a shit place. The reason it has not caused more of an outdry or worry (in the West) is, that we have also been indoctrinated that all of Islam is basically"mad". or backward or ... so. If you compare what Iran looked like in the 70ties and now, it has gone backwards by leaps and bounds. I see the same awful thing happening now in the USA - except the taliban carry a cross and a flag. this guy knows it better than I do: [fareedzakaria.com]

The PLO started what's considered modern terrorism.

The big bully that lived around the corner from me when I was a little kid.

Terrorism is always in the eyes of the beholder just like beauty it is a matter of one's perspective. Americans and their allies like to label anyone that opposes they world view as terrorists even states get the label.
It is a nice label that is used to dehumanize the enemy by any government but, in reality the only real terrorists are those that live only for wealth and the power it grants them.

"Terrorism" is the act of freedom fighters who have yet to win their battle and reframe the discussion - at least in their eyes.

Terrorism has been around probably since man took up arms against other men. It's a successful tool to use against an enemy who is larger and stronger. The movie Apocalypse Now describes it fairly well. Another well-known example is Vlad Tepes better know as Vlad the Impaler. He was tasked with defending his principality against a much larger stronger army, the Turks.

Terrorism has existed as long as there have been ideological zealots-- particularly if they are out of power or feel discriminated against. A more productive question is: What can we do to prevent people from deciding to be terrorists?

God. If one believes in such things. Think as I direct, behave as I direct, believe as I direct or I will torture you, gaslight you, and then, like the stalker from hell, make life without me an eternity of pain. Sounds like a terrorist to me...

How Far back do you want me to go?

The tactic has been around a long time.

I think the first known terrorists were the ones to attack the Israeli athletes at the Munich Olympics. Or the first hijackings? Anyone?

Religion. More specifically, people using their own religion to tell others how to live their own lives.

Humans