From BiblePortal Wikipedia

Hastings' Dictionary of the Bible [1]

Gederothaim occurs in   Joshua 15:36 as one of the fourteen cities of Judah that lay in the Shephçlah. There are, however, fourteen cities without it, and it is probable that the name has arisen by dittography from the preceding Gederah . The subterfuge of the AVm [Note: Authorized Version margin.] ‘Gederah or Gederothaim’ is not permissible.

Holman Bible Dictionary [2]

 Joshua 15:36Gederah

Morrish Bible Dictionary [3]

City in the lowlands of Judah.  Joshua 15:36 .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [4]

(Heb. Gederotha'yim, גְּדֵרוֹתִיַם , Two Folds (See Geder); Sept. omits, but some copies translate Αἱ Ἐπαύλεις Αὐτῆς , Vulgate Gederothaim), the name of a town in the plain of Judah ( Joshua 15:36), mentioned in connection with GEDERAH (See Gederah) (q.v.); where, probably, instead of rendering the copulative ו "and," we should (with the margin) translate it "or," since otherwise there would be 15 instead of 14 cities enumerated, as stated in the text. So Schwarz (Palest. page 103), who, however, confounds it with Gederoth, and even with the Gazara (q.v.) of the Apocrypha (see Reland, Palaest. page 778).

International Standard Bible Encyclopedia [5]

ged - ē̇ - rō̇ - thā´im ( גּדרתים , gedhērōthayim , "place of enclosures"): Stands as the 15th in a list which professes to give only the names of 14 cities in the Judean Shephelah (  Joshua 15:36 ). the King James Version margin suggests that we might read "or" for "and" after Gederah, but this is impossible. Septuagint reads, "and its cattle shelters." Probably, however, the name has arisen by dittography from the preceding Gederah (which see).