barnacle \bar"nacle\, n. prob. from e. barnacle a kind of
   goose, which was popularly supposed to grow from this
   shellfish; but perh. from ll. bernacula for pernacula, dim.
   of perna ham, sea mussel; cf. gr. pe`rna ham. cf. f.
   bernacle, barnacle, e. barnacle a goose; and ir. bairneach,
   barneach, limpet. zool.
   any cirriped crustacean adhering to rocks, floating timber,
   ships, etc., esp.
   a the sessile species genus balanus and allies, and
   b the stalked or goose barnacles genus lepas and
       allies. see cirripedia, and goose barnacle.
       1913 webster

   barnacle eater zool., the orange filefish.

   barnacle scale zool., a bark louse ceroplastes
      cirripediformis of the orange and quince trees in
      florida. the female scale curiously resembles a sessile
      barnacle in form.
      1913 webster
see also:
balanus lepas cirripedia goose barnacle barnacle eater barnacle scale 
ceroplastes cirripediformis