The compound Balchoth consists of Westron balc ("horrible") + Sindarin hoth ("horde"). It was actually a generic term for cruel peoples, including the Orcs.
Sindarin
balchoth
collective name. *Horrible-horde
Elements
Word Gloss balc “horrible” hoth “host, horde, host, horde, [N.] crowd; group plural; [ᴱN.] folk, [G.] people; †army”
Balchoth
Balchoth
A tribe of Easterlings that invaded the lands of Gondor in the middle of the 3rd Age (LotR/1053). The name was a combination of Wes. balc “horrible” and S. hoth “horde” (UT/313 note #24).