From BiblePortal Wikipedia

Smith's Bible Dictionary [1]

Hid'dekel. (Rapid). One of the rivers of Eden, the river which "goeth eastward to Assyria,"  Genesis 2:14, and which Daniel calls, "the great river,"  Daniel 10:4, seems to have been rightly identified by the Septuagint (LXX) with the Tigris. Dekel is clearly an equivalent of Digla or Dighath, a name borne by the Tigris in all ages. The name now in use among the inhabitants of Mesopotamia is Dijleh .

Hastings' Dictionary of the Bible [2]

Hiddekel . The river Tigris, mentioned as the third river of ParadiseGenesis 2:14 ), and as ‘the great river’ by the side of which Daniel had his vision (  Daniel 10:4 ). The Heb. Hiddeqel was taken from the Bab. [Note: Babylonian.] name for the Tigris, Idiglat or Diglat , which was in turn derived from its Sumerian name, Idigna .

L. W. King.

People's Dictionary of the Bible [3]

Hiddekel ( Hĭd'De-Kĕl ), Rapid. One of the rivers of Eden, the river which "goeth eastward to Assyria,"  Genesis 2:14, and which Daniel calls "the great river,"  Daniel 10:4, rightly identified with the Tigris. The name now in use among the inhabitants of Mesopotamia is Dijleh.

Fausset's Bible Dictionary [4]

Tigris. A river of Eden, going "eastward to Assyria" ( Genesis 2:14). (See Eden .) "The great river" ( Daniel 10:4). From Hai "lively," and Digla "an arrow," in early Babylonian; equivalent to Tigra in Aryan. Now called by the Arabs Dijleh .

Morrish Bible Dictionary [5]

One of the rivers of Eden: supposed to be identical with the Tigris, which is called Dijlah.  Genesis 2:14;  Daniel 10:4 .

Holman Bible Dictionary [6]

 Genesis 2:14

KJV also retains the transliteration for Tigris in  Daniel 10:4 . See Tigris.

American Tract Society Bible Dictionary [7]

One of the rivers of Paradise. Its modern name is Tigris. See Eden , and Euphrates .

Easton's Bible Dictionary [8]

 Genesis 2:14

Watson's Biblical & Theological Dictionary [9]

See Eden .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [10]

(Heb. Chidde'kel, חַדֶּקֶל , in pause Chid, Da'Kel, חַדּ קֶל ; Sept. Τίγρις , to which in  Daniel 10:4 it adds Ε᾿Νδεκέλ v.r. Ε᾿Δδεκέλ ; Vulg. Tigris), the name of the third of the four rivers of Paradise, being that which runs on the border ( קַדנְמִת ) of Assyria ( Genesis 2:14), and "the great river" on the banks of which Daniel received his remarkably minute vision, or, rather, angelic prediction of the mutual history of Egypt and Syria (Daniel 2, 4). There has never been much dispute of the traditional interpretation which identifies the Tigris with the Hiddekel. According to Gesenius (Thesaur. p. 448), this river in Aramsean is called Digla, in Arabic Diglat, in Zendl Teger, in Pehlvi Teyera, "stream;" whence have arisen both the Aramaean and Arabic forms, to which also we trace the Hebrew Dekel divested of the prefix Hid. This prefix denotes activity, rapidity, vehemence, so that Hid-dekel signifies " he rapid Tigris." From the introduction of the prefix, it would appear that the Hebrews were not entirely aware that Teger, represented by their דקל , Dekel, by itself signified velocity; so in the language of Media, Tigris meant an Arrow (Strabo, 2, 527; Pliny, Hist. Nat. 6: 27; comp. Persic Teer, "arrow;" Sanskrit Tigra, "sharp," "swift"); hence arose such pleonasms as "king Pharaoh" and "the Al-coran." First, however (Heb. Lex. s.v.), regards the Last syllable as a mere termination to an original form חַדֵּק , Hiddek, from חָדִק , to Be Sharp, hence to flow swiftly. "The form Diglath occurs in the Targums of Onkelos and, Jonathan, in Josephus (Amnt. 1, 1), in the Armenian Eusebius (Chronicles Can. pt. 1, c. 2), in Zonaras (Ann. 1, 2), and in the Armenian version of the Scriptures. It is hardened to Diglit (Diglito) by Pliny (Hist. Nat. 6, 27). The name now in use among the inhabitants of Mesopotamia is Dijleh. It has generally been supposed that Higla is a mere Shemitic corruption of Tigra, and that this latter is the true name of the stream; but it must be observed that the two forms are found side by side in the Babylonian transcript of the Behistun inscription, and that the ordinary name of the stream in the inscriptions of Assyria is Tiggar. Moreover, if we allow the Dekel of Hid-dekel to mean the Tigris, it would seem probable that this was the more ancient of the two appellations. Perhaps, therefore, it is best to suppose that there was in early Babylonian a root dik, equivalent in meaning, and no doubt connected in origin, with the Arian tig or tij, and that from these two roots were formed independently the two names, Dekel, Dikla, or Digla, and Tiggar, Tigra, or Tigris. The stream was known by either name indifferently; but, on the whole, the Arian appellation predominated in ancient times, and was that most commonly used even by Shemitic races. The Arabians, however, when they conquered Mesopotamia, revived the true Shemitic title, and this (Dijleh) continues to be the name by which the river is known to the natives down to the present day."

The Tigris rises in the mountains of Armenia, about fifteen miles south of the sources of the Euphrates, and pursues nearly a regular course south- east till its junction with that river at Korna, fifty miles above Basrah (Bassorah). The Tigris is navigable for boats of twenty or thirty tons' burden as far as the mouth of the Odorneh, but no further; and the commerce of Mosul is consequently carried on by rafts supported on inflated sheep or goats' skins. (See Float).

These rafts are floated down the river, and when they arrive at Baghdad the wood of which they are composed is sold without loss, and the skins are conveyed back to Mosul by camels. The Tigris, between Baghdad and Korna, is, on an average, about two hundred yards wide; at Mosul its breadth does not exceed three hundred feet. The banks are steep, and overgrown for the most part with brushwood, the resort of lions and other wild animals. The middle part of the river's course, from Mosul to Korna, once the seat of high culture and the residence of mighty kings, is now desolate, covered with the relics of ancient greatness in the shape of fortresses, mounds, and dams, which had been erected for the defense and irrigation of the county. At the ruins of Nimrud, eight leagues below Mosul, is a stone dam quite across the river, which, when the stream is low, stands considerably above the surface, and forms a small cataract; but when the stream is swollen, no part of it is visible, the water rushing over it like a rapid, and boiling up with great impetuosity. It is a work of great skill and labor, and now venerable for its antiquity. The inhabitants, as usual, attribute it to Nimrod. It is called the Zikr ul-Aawaze. At some short distance below there is another Zikr (dike), but not so high, and more ruined than the former. The river rises twice in the year: the first and great rise is in April, and is caused by the melting of the snows in the mountains of Armenia; the other is in November, and is produced by the periodical rains. (See Kinneir, Geog. Mem. Of Persian Empire, p. 9, 10; Rich's Koordistan; Chesney's Euphrates Expedition; Sir R. K. Porter's Travels; etc.) (See Tigris).

International Standard Bible Encyclopedia [11]

hid´ē̇ - kel ( חדּקל , ḥiddeḳel ): One of the rivers of Eden (which see) ( Genesis 2:14 , the Revised Version margin "that is, Tigris"; so Septuagint Τίγρις , Tı́gris ), said to flow East to Assyria, usually identified with the Tigris, which rises in Armenia near Lake Van and, after flowing Southeast through 8 degrees of latitude, joins the Euphrates in Babylonia to form the Shatt el - 'Arab , which runs for 100 miles through a delta which has been formed since the time of Abraham, and now enters the Persian Gulf through 2 branches. About one-third of the distance below its source, and soon after it emerges from the mountains of Kurdistan, the Tigris passes by Mosul, the site of ancient Nineveh, and, lower down at Bagdad, approaches within a few miles of the Euphrates. Here and for many miles below, since the level is lower than that of the Euphrates, numerous canals are conducted to it, irrigating the most fertile portions of Babylonia.