any of numerous species of marine crustaceans that are is free-swimming as a larvae but fixed to rocks or floating objects as an adults: class Cirripedia
often used figuratively to convey tenacious attachment
From that hour I clove to Queequeg like a barnacle — Herman Melville
barnacled adj
from the former belief held from at least the 12th cent. to the 17th cent. that barnacle geese hatched from barnacles growing on trees or attached to waterlogged timbers. The mistake probably partly arose from the mystery of the goose's origin (it was not known that they breed in the Arctic). The name of the bird was therefore transferred to the marine animal in the 16th cent