https://www.oed.com/view/Entry/85431?rskey=k6...
heel
n. The end at which the bow of a stringed instrument is held. Opposed to point n.1 19d.
1842 J. A. Hamilton Dict. Mus. Terms (new ed.) 85 Talon,..The heel of the bow, that part near the nut.
1856 M. C. Clarke tr. H. Berlioz Treat. Mod. Instrumentation 12 With the heel [Fr. talon] of the [violin] bow.
1915 J. Dunn Violin Playing (ed. 3) viii. 50 The third example can also be taken at the heel, commencing down bow, when the bow will be raised for the accented notes as at the point.
1987 D. C. Pratt & C. Bunting 'Cello Technique v. 12 Proceed similarly with the up-bow until about four inches from the heel.
2009 A. Barlowe 12 Etude-caprices 9 The easiest places to check levels are at the middle and the heel of the bow.
https://en.wikipedia.org/wiki/Violin#Bows
A violin is usually played using a bow consisting of a stick with a ribbon of horsehair strung between the tip and frog (or nut, or heel) at opposite ends.
https://www.duden.de/rechtschreibung/Frosch
Griffende des Bogens von Streichinstrumenten, das mit einer Stellschraube zum Spannen der Saiten versehen ist; Talon (3)
http://www.bildwoerterbuch.com/en/arts-and-ar...
The Bogenansatz is shown as the very bottom bit of the bow, encompassing the frog/grip/nut.
https://www.badische-zeitung.de/der-frosch-au...
Wieso heißt der Frosch, an dem ein Geiger den Bogen hält, Frosch?
Dafür gibt es zwei Erklärungen: Ein Grund ist, dass der Frosch eine maulähnliche Öffnung hat. Außerdem wurde der Frosch bei Barockbögen nur aufgesetzt und konnte deshalb leicht "weghüpfen".
https://dictionary.onmusic.org/terms/4948-heel
heel [English]
Another term for frog.
https://www.violinonline.com/bowingeffects.html
Au talon: Talon is French for heel, and the term au talon, “at the heel,” means play the music with the bow hair at the heel or bottom part of the bow, closest to the hand (other terms for playing music using the bottom part of the bow include "at the frog" or nut).
http://www.users.globalnet.co.uk/~leonid/play...
Playing at the heel and other notes about teaching
An awkward place to be for some : Some violinists aren’t comfortable at the heel. Perhaps they stopped going all the way to heel, some time ago. There may be 2 inches of greasy bow hair at the heel which has no rosin, and slips on the string .... another indication that the owner of that bow doesn’t play at the heel.
https://www.oed.com/view/Entry/85431?rskey=k6...
s. On a guitar, violin, or similar stringed instrument: the point at which the neck is attached to the body of the instrument.
1909 Common-sense June 8 (advt.) Mandolin... Natural mahogany finished neck with shaped heel and head.
1978 Early Music 6 533/1 The ribs [of the viol] have been cut down to taper evenly from the heel to the end.
2003 P. F. Gura C. F. Martin & his Guitars iii. 106 He..commonly used what is known as a Spanish-shaped heel rather than the ice cream cone shape typical of his earlier instruments.
