The Collaborative International Dictionary of English v.0.48:

Ballarag \Bal"la*rag\ (b[a^]l"l[.a]*r[a^]g), v. t. [Corrupted
   fr. bullirag.]
   To bully; to threaten. [Low] --T. Warton.

   Syn: bullirag; bullyrag. [1913 Webster]