The Collaborative International Dictionary of English v.0.48:

Boanerges \Bo`a*ner"ges\ [Gr. ?, fr. Heb. bn[=e] hargem sons of
   thunder. -- an appellation given by Christ to two of his
   disciples (James and John). See Mark iii. 17.]
   Any declamatory and vociferous preacher or orator.
   [1913 Webster]

Easton's 1897 Bible Dictionary:

Boanerges
sons of thunder, a surname given by our Lord to James and John
(Mark 3:17) on account of their fervid and impetuous temper
(Luke 9:54).

Hitchcock's Bible Names Dictionary (late 1800's):

Boanerges, son of thunder