It is archaic terminology for a spur ('dard' in French, 'dart' in English).

Ok, so the copy that I had been reading was the digital version hosted by Cornell. It's in a terrible format and not very readable, so I completely missed the section written by the translator, who explains the terminology.

I've since found a physical copy from the library which is much more readable.

As it turns out, a dard is,

" a bud which has not grown beyond a certain point and which is surrounded by a rosette of two or three small leaves. It is the sign of fruitfulness in the pear. This small pointed growth can easily turn into a shoot if it receives too much sap. But in ordinary circumstances, the dard, under the steady stimulus of the sap which is regularly distributed throughout all the branches of the tree, swells and adds to itself a rosette of leaves, which gradually increase in number from three to five. Continuing to develop, the dard is finally crowned with seven leaves and is then known as a fruit spur (lambourde).

I have a copy of that book and it is hard to follow and I needed to refer to it periodically thru the process. I tried the system last summer on a few apple trees and I will see this spring if it worked. I can say, that the practice he talks about of heading back the main shoot does result in fruiting spurs starting to develop farther down the branch. I now have dards forming.

With the Lorette book and the teaching of Dr. Stefano Musacchi, who uses the "click" form of pruning, it comes a little clearer. He explains the dard etc. a little better.

If you don't like to click on links, just go to you tube and type in

Dr. Stefano Musacchi click pruning.

pruning bartlett pear to optimize fruit quality