A trencherman obviously comes from the other trencher[sup]1[/sup].In Play:The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
trench
PRONUNCIATION: trĕnch
NOUN: 1. A deep furrow or ditch. 2. A long narrow ditch embanked with its own soil and used for concealment and protection in warfare. 3. A long, steep-sided valley on the ocean floor.
VERB: Inflected forms: trenched, trench·ing, trench·es
TRANSITIVE VERB: 1. To cut a trench in. 2. To fortify with trenches. 3. To place in a trench. 4. To make a cut in; carve.
INTRANSITIVE VERB: 1. To dig trenches or a trench. 2. To verge or encroach. Often used with on or upon.
ETYMOLOGY: Middle English trenche, from Old French, from trenchier, to cut, perhaps from Vulgar Latin *trincāre, variant of Latin truncāre, from truncus, trunk. See ter-[sup]2[/sup] in Appendix I.
trenchant
SYLLABICATION: trench·ant
PRONUNCIATION: trĕn'ch
ADJECTIVE: 1. Forceful, effective, and vigorous: a trenchant argument. See synonyms at incisive. 2. Caustic; cutting: trenchant criticism. 3. Distinct; clear-cut.
ETYMOLOGY: Middle English, from Old French, cutting, from present participle of trenchier, to cut. See trench.
OTHER FORMS: trench'an·cy —NOUN
trench'ant·ly —ADVERB
trencher[sup]1[/sup]
SYLLABICATION: trench·er
PRONUNCIATION: trĕn'ch
NOUN: 1. A wooden board or platter on which food is carved or served. 2. Archaic The pleasure of the table; food.
ETYMOLOGY: Middle English trenchur, from Anglo-Norman trenchour, from trencher, to cut, perhaps from Vulgar Latin *trincāre. See trench.
trencher[sup]2[/sup]
SYLLABICATION: trench·er
PRONUNCIATION: trĕn'ch
NOUN: One that digs trenches.
trencherman
SYLLABICATION: trench·er·man
PRONUNCIATION: trnchr-mn
NOUN: 1. A hearty eater. 2. Archaic One who frequents another's table; a hanger-on or parasite.
The American Heritage® Dictionary of the English Language, Fourth Edition. Copyright © 2000 by Houghton Mifflin Company. Published by the Houghton Mifflin Company. All rights reserved.
From the Internet Movie Data Base biography of the late Fred Gwynne:
Hmmm. Seafood Gumbo soup in the cafeteria today . . .In 1955, he made a memorable guest appearance as Private Honigan on The Phil Silvers Show (1955). He played a soldier with an enormous appetite that Silvers' Sgt. Bilko entered into a pie-eating contest, only to discover he could only eat like a trencherman when he was depressed. The spot lead to him coming back as a guest in more episodes.
Oh, well, he wasn't the lead on that show.