underbearer

from The Century Dictionary.

• noun One who helps to carry the corpse and accessories at a funeral.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who supports or sustains; especially, at a funeral, one of those who bear the corpse, as distinguished from a bearer, or pallbearer, who helps to hold up the pall.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun One who helps to bear or carry the corpse or accessories at a funeral.