From BiblePortal Wikipedia

Fausset's Bible Dictionary [1]

( Genesis 10:21-24. Professor Rawlinson translates: "unto Shem also, the father of all the children of Eber, the elder brother of Japhet, were children born, Arphaxad":  Genesis 11:10) ("the stronghold of the Chaldees".) Shem's descendants are mentioned last, because the subsequent sacred history concerns them chiefly. His being forefather to Eber or Heber is specified, to mark that the chosen people of God, the Hebrew, sprang from Shem: Arphaxad was father of Salah. There was a portion of Assyria called Arrapachitis, from Arapkha, "the city of the four sacred fish," often seen on cylinders; but the affinity is doubtful.

Smith's Bible Dictionary [2]

Arphax'ad. (Stronghold Of The Chaldees).

1. The son of Shem and ancestor of Eber.  Genesis 10:22;  Genesis 10:24;  Genesis 11:10.

2. Arphaxad, a king "who reigned over the Medes in Ecbatana,"  Judith 1:1-4; perhaps the same as Phraortes, who fell in a battle with the Assyrians, 633 B.C.

Hastings' Dictionary of the Bible [3]

ARPHAXAD . 1 . A king of the Medes ( Jdt 1:1 ff.). He reigned at Ecbatana, which he strongly fortified. Nebuchadrezzar, king of Assyria, made war upon him, defeated him, and put him to death. 2 . The spelling of Arpachshad in AV [Note: Authorized Version.] , and at   Luke 3:36 by RV [Note: Revised Version.] also. See Arpachshad.

Morrish Bible Dictionary [4]

Son of Shem, born two years after the flood, from whom Abraham descended.  Genesis 10:22,24;  Genesis 11:10-13;  1 Chronicles 1:17,18,24 . Stated as the father of Cainan in  Luke 3:36 . See CAINAN.

American Tract Society Bible Dictionary [5]

A son of Shem, two years after the flood,  Genesis 10:22;  11:10 . Seven generations followed him before Abraham, while he lived till after the settlement of Abraham in the land of promise and the rescue of Lot from the four kings. He died A. M. 2096, aged four hundred and thirty-eight.

Hastings' Dictionary of the New Testament [6]

ARPHAXAD. —The spelling (in both Authorized Version and Revised Version NT 1881, OT 1885 of  Luke 3:36) of the OT name which appears more correctly in the Revised Version NT 1881, OT 1885 of OT as Arpachshad .

Easton's Bible Dictionary [7]

 Genesis 11:10-13 1 Chronicles 1:17,18 Luke 3:36

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [8]

(Heb. Arpakshad', אִרְפִּכְשִׁד [on the signif. see below]; Sept. and N.T. Ἀρφαξάδ , Josephus Ἀρφαξάδης ) , the name of two men.

1. The first postdiluvian patriarch, son of Shem, and father of Salah; born one year after the end of the Deluge, and died B.C. 2075, at the age of 438 years ( Genesis 11:10-13;  1 Chronicles 1:17-18;  Luke 3:36). From  Genesis 10:22;  Genesis 10:24, it appears that the region settled by this patriarch's descendants likewise took his name. The conjecture of Bochart (Pkaleg, ii, 4) has been adopted by several others (Michaelis, Suppl. p. 129; Orient. Bibl. 17:77 sq.; Mannert, v, 439), that it is the province Arrhapachitis ( Ἀῤῥαπαχῖτις ) , in northern Assyria, near Armenia (Ptol. 6:1), the primitive country of the Chaldaeans (Josephus, Ant. i, 6, 4; comp. Syncell. Chronicles p. 46), whose national title ( כִּשְׂדִּים , Kasdin) appears to form the latter part of the name Arphaxad ( כְּשִׂד ); the first part being referred by Michaelis (Spicileg. i, 73 sq.) to an Arabic root signifying Boundary (q. d. "border of the Chaldaeans"), but with as little felicity (see Tuch, Genesis p. 256) as the derivation by Ewald (Isr. Gesch. i, 333) from another Arabic root signifying to Bind (q. d. "fortress of the Chaldaeans"). (See Gesenius, Commentar Ub. Jesa. 23: 13; and comp. Niebuhr, Gesch. Assur'S, p. 414, note.) Bohlen (Genesis in loc.), with even less probability, compares the Sanscrit Arjapakshata " (a land) by the side of Asia;" comp. Porussia, i. q. Po-Rus, i.e. near the Russians. (See Schlozer in the Repert. F. Bibl. Lit. 8: 137; Lengerke, Kenaan, i, 211; Knobel, Volkertofel D. Genesis, Giess. 1850.)

2. A king of Media at Ecbatana, which city he had fortified during an open campaign and siege'by his contemporary Nebuchadnezzar (Judith i, 1 sq.). From the connection of his name with Ecbatana he has been frequently identified with Deioces (Ctes. "Artaeus"), the founder of Ecbatana (Herod. i, 98); but as Deioces died peaceably (Herod. i, 102), it seems better to look for the original of Arphaxad in his son Phraortes (Ctes. "Artynes"), who greatly extended the Median empire, and at last fell in a battle with the Assyrians, B.C. 633 (Herod. i, 102). But this would disagree with the date and circumstances of Nebuchadnezzar; moreover, the half-fabulous book of Judith abounds with statements respecting the Median kings scarcely reconcilable with genuine history. (See Media); (See Judith). Niebuhr (Gesch. Assur'S, p. 32) endeavors to identify the name with "Astyages" =Ashdahak, the common title of the Median dynasty, and refers the events to a war in the twelfth year of Nebuchadnezzar, king of Babylon, B.C. 592 (Ibid. p. 212, 285). (See Nebuchadnezzar).

International Standard Bible Encyclopedia [9]

ar - fak´sad  : (1) The King James Version form ( Genesis 10:22 ,  Genesis 10:24;  Genesis 11:12 ,  Genesis 11:13;  1 Chronicles 1:17 ) of the Revised Version (British and American) Arpachshad . See also Table Of Nations . (2) In Apocrypha (Judith 1) a king of the Medes, who reigned in Ecbatana. He was defeated and slain by Nebuchadrezzar.

Kitto's Popular Cyclopedia of Biblial Literature [10]

Arphax´ad, the son of Shem, and father of Salah; born one year after the Deluge, and died B.C. 1904, aged 438 years ( Genesis 11:12, etc.).