CXXXV. These are three sorts of Chissels, the first is the Paring Chissel, this hath a very fine smooth edge; its office is to follow the Former, and to pare off the Irregularities the Former doth make; but of this see more chap. 9. numb. 1.
The second is termed a Former, it is a Chissel used before the Paring Chissel in all works, even as the Fore Plain is used before the Smoothing Plain, when it is used the Helve of it is knockt upon with the Mallet, to drive the edge of it into the Stuff: There are several Sizes of these kind of Chissels, from a quarter of an Inch, to an Inch and half broad.
The third is another kind of Chissel of the nature of a Former, only it is broad at the Basil or edge part, and groweth taper all along after till it comes to the shouldering; of these there are diverse Sizes, from half or quarter of an Inch, to an Inch and half, and have their terms according to their breadth, as an half Inch Former, an Inch Former, &c.
The proper posture for these kind of Tools are to have their edges or cutting part downwards, if otherwise then to be mentioned.
S. a Fess between 2 such the Basils erected, and a third A. Hasts· O. born by the name of Former.
— From Randle Holme’s “The Academy of Armory, or, A Storehouse of Armory and Blazon” Book III, Chapter VIII, Plate 2.
I hate to ask the obvious but do you suspect the contemporary term "firmer chisel" is a corruption of "former"?