From BiblePortal Wikipedia

Hastings' Dictionary of the Bible [1]

Kadmonites . One of the nations whose land was promised to Abram’s seed (  Genesis 15:19 ). Their habitat was probably in the region of the Dead Sea. The fact that Kedemah is said to be a son of Ishmael (  Genesis 25:15 ) renders it likely that they were Ishmaelite Arabs. Ewald, however, regarded Qadmoni as equivalent to B e ne Qedhem (‘Sons of the East’) which seems to have been a general name applied to the Keturahite tribes (see   Genesis 25:1-6 ).

W. M. Nesbit.

American Tract Society Bible Dictionary [2]

 Genesis 15:19 , a tribe of Canaanites who inhabited the promised land east of the Jordan, about mount Hermon. Some have fancied that Cadmus, the supposed inventor of the Greek alphabet, and who came from the East, was a Kadmonite. If so, he only introduced into Greece the alphabet of his own country, since the Greek letters are obviously derived from the Phoenician or ancient Hebrew letters.

Watson's Biblical & Theological Dictionary [3]

ancient inhabitants of the land of Canaan, whose habitation was beyond Jordan, to the east of Phenicia,  Genesis 15:19 . The Kadmonites were descended from Canaan, the son of Ham. It has been conjectured that the celebrated Cadmus, the founder of Thebes in Boeotia, was originally a Kadmonite; and that his wife, Hermione, was so named from Mount Hermon.

Morrish Bible Dictionary [4]

One of the ancient peoples who possessed the land promised to Abraham.  Genesis 15:19 . Probably the same as bene-Kedem, 'children of the east.'  Judges 6:3 .

Fausset's Bible Dictionary [5]

From Kedem," children of the East," the tribes roaming in the wilds S. and S.E. of Palestine.

Easton's Bible Dictionary [6]

 Genesis 15:19

Kitto's Popular Cyclopedia of Biblial Literature [7]

Kad´monites, one of the nations of Canaan, which is supposed to have dwelt in the north-east part of Palestine, under Mount Hermon, at the time that Abraham sojourned in the land . It is supposed that the name denotes 'an eastern people,' and that they were situated to the east of the Jordan, or rather that it was a term applied collectively, like 'Easterns,' or 'Orientals,' to all the people living in the countries beyond that river.