What does the word tora tora tora mean in Japanese?

first answer:

It is a contraction of totsugeki raigeki (lightning attack). To ra.

It originated at the Japanese attack on Pearl Harbor.

second answer:

"Tora" as pronounced is also the Japanese word for "tiger". The word "Tora" is actually intended to be 2-part codeword that is saying that surprise has been achieved in the Japanese attack on Oahu Island (including Pearl Harbor).