Tadpoles are small water creatures which grow into frogs or toads.
tadpole in British English
(ˈtædˌpəʊl)
noun
the aquatic larva of frogs, toads, etc, which develops from a limbless tailed form with external gills into a form with internal gills, limbs, and a reduced tail
Word origin
C15 taddepol, from taddetoad + pol head, poll
tadpole in American English
(ˈtædˌpoʊl)
noun
1.
the larva of certain amphibians, as frogs and toads, having gills and a tail and living in water: as it matures, the gills usually are lost and legs develop
2.
the free-swimming larval stage of tunicates, having gill slits and a notochord
Word origin
ME taddepol < tadde, toad + poll, head, hence, toad that seems all head