a silver variety of the goldfish Carassius auratus
any of various other silvery fishes, such as the moonfish Monodactylus argenteus
any of various small primitive wingless insects of the genus Lepisma, esp L. saccharina, that have long antennae and tail appendages and occur in buildings, feeding on food scraps, bookbindings, etc: order Thysanura (bristletails)
1703, in reference to various types of silver-colored fish (cf. German Silberfisch, Dutch zilvervisch); from silver + fish (n.). In reference to a type of household insect damaging to books, wallpaper, etc. (also known as silvertail and furniture-bug), it is attested from 1855.