From BiblePortal Wikipedia

Hastings' Dictionary of the Bible [1]

Gabatha . One of two eunuchs whose plot against Artaxerxes (the Ahasuerus, i.e. Xerxes, of canonical Est.) was discovered and frustrated by Mardocheus (Mordecai). Ad. Est 12:1. In   Esther 2:21 he is called Bigthan and in   Esther 6:2 Bigthana .

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [2]

( Γαβαθά ), one of the eunuchs of king Xerxes, the exposure of whose plots by Mardochaeus led to their execution (Esth. 12:1, Apocr.); evidently the BIGTHAN (See Bigthan) (q.v.) of the Heb. text ( Esther 2:21).

International Standard Bible Encyclopedia [3]

gab´a - tha ( Γαβαθά , Gabathá ): A eunuch of Mardocheus (Additions to Esther 12:1).