crabber

From crab (“crustacean having five pairs of legs”) +‎ -er (occupational suffix) or +‎ -er (relational noun suffix).

crabber (plural crabbers)

1. A person who catches crabs.
   • 1989, National Fisherman (volumes 70-71, page 26)

     Many shrimpers complain that the crabbers place their traps too close together and that they can't go between the traps without snagging their nets.

2. (nautical) A boat used for catching crabs.
   • 1972, Ursula K. Le Guin, The Farthest Shore

     In the bright haze of morning they came into Hort Harbor, where a hundred craft were moored or setting forth: fishermen's boats, crabbers, trawlers, trading-ships, two galleys of twenty oars […]

From crab (“to be ill-tempered; to complain or find fault”) +‎ -er.

crabber (plural crabbers)

1. A person who finds fault or criticizes.
   • 1936, Josephine Tey, A Shilling for Candles, New York, NY: Simon & Schuster, published 1998, →ISBN, page 103:

     There were one or two crabbers, of course—people who wanted his job—but no one paid any attention to the likes of them.

   Synonyms: criticizer; see also Thesaurus:complainer