Hiddekel

"Called by the Accadians id Idikla; i.e., "the river of Idikla"," the third of the four rivers of Paradise (Gen. 2:14). Gesenius "interprets the word as meaning "the rapid Tigris." The Tigris" "rises in the mountains of Armenia, 15 miles south of the source" "of the Euphrates, which, after pursuing a south-east course, it" "joins at Kurnah, about 50 miles above Bassorah. Its whole length" "is about 1,150 miles."

Definition of Hiddekel:
"sharp voice; sound"