An Etymological Dictionary of the German Language/Annotated/Frosch
Frosch, masculine, ‘frog,’ from the equivalent Middle High German vrosch, Old High German frosk, masculine; corresponding to Dutch vorsch, Anglo-Saxon forsc (English dialectic frosk), Old Icelandic froskr, ‘from’; Gothic *frusqa- is by chance not recorded. Before the derivative sk a guttural has dropped out, as is seen in the cognate terms. Anglo-Saxon frogga, English frog, would be in Gothic *frugga (*frugwa?); also akin to Anglo-Saxon frocca, earlier English dialectic frock, as well as Old Icelandic fraukr, ‘frog’ (so too Middle English frûte, froute, ‘toad’). Gothic *frusqa-, for *fruhsqa-, therefore be connected with a root ending in a guttural; perhaps the pre-Teutonic root pruk?. Hence the attempts to connect the word with frisch or frieren, to which the meaning is also opposed, must be rejected.