Tadpole
Tadpole , noun
[Old English tadde toad (Anglo-Saxon tādie, tādige) + poll; properly, a toad that is or seems all head. See Toad, and Poll.]
1.
(Zoology) The young aquatic larva of any amphibian. In this stage it breathes by means of external or internal gills, is at first destitute of legs, and has a finlike tail. Called also polliwig, polliwog, porwiggle, or purwiggy.
2.
(Zoology) The hooded merganser. [Local, United States]