Why is a Frog Called a Frog?

Excerpts from The Messageboards

Erik S. Friis asked: I'm currently reading Garrett Hack's Handplane Book and enjoying it, but I'm interested in some of the terms that evolved for handplanes and their parts. Like why was a frog called a frog?

Also curious about the historical names for pitch, common, York, middle, half. York is perhaps obvious in that it may have been commonly used by planers and/or plane makers in the English city of York. But why is 60° called half and not 45? It seems that there's some rather interesting history behind them. Is there a book that gets deeper into this historical perspective?

David Barnett - Venice, Florida: Something frogged is braced or supported firmly. Possibly derived from the Portuguese froco when used as fastener. Frogs are found in clothing. Military uniforms are often fastened with frogs. The use of frog to describe a fastener or an object used to hold fast (frogs on rigging, the frog nut on violin bows), is likely very old. Also, the horny triangular section of a horse hoof is called a frog, somewhat similar in shape to a Bailey frog, I suppose. Perhaps likely for iron planes is the ribbed supporting plate used for track switching. Of course, the chosen term frog is again used in the sense of support, holding fast, etc.

Joel: As far as I know the term only relates to metal planes with a moveable blade support. I cannot recall seeing it in any other literature. That is, of course, this means the term only dates to the 1850s or so. A good question is the earliest appearance of the word in any literature. A trip to the Oxford English Dictionary is probably in order. An obvious root might be the a plane has a throat and, well, with a moveable base, you got a frog in your throat.

David Barnett - Venice, Florida: …the O.E.D. is lacking in examples, pedigree, provenance, and etymology for frog as positioner, fastener, brace, nut, support, fulcrul tensioner, jamb, and wedge, my apologies to Dr. Johnson. Of course, I spared the questioner on derivation of froco from an earlier linguistic floco, from Latin floccus, referring to wool, fuzz, nap, and tuft, from which the verb flock is derived, such as “to flock the inside of a box.” Then there's frock, similar to the Portugese. froco, which is a sort of shift, which in a shortened version is called by the Scots a cutty sark, which has nothing to do with anything beyond my drinking scotch of a distinction far better than the aforementioned as I type.

Frog as holdfast is thesaurically supported, however (couldn't resist). Gonna have to spring (hop?) for a breeding pair of those nifty new frogs of yours, Joel.

Ed. note with apology: All of the above is most erudite and interesting, but misses the simple explanation. It just looks just like a frog!