The Collaborative International Dictionary of English v.0.48:

Boss \Boss\ (b[o^]s), v. t. [imp. & p. p. Bossed (b[o^]st); p.
   pr. & vb. n. Bossing.] [OE. bocen, fr. OF. bocier. See the
   preceding word.]
   To ornament with bosses; to stud.
   [1913 Webster]