Bowing On The String
Tartini beautifully described how to develop the technique of playing détaché the separated stroke on the string; in his letter to Countess Lombardini, from 1771. He instructed her to "play your Corelli allegro, in the last inch of the bow, with a rest between each note", and then said "When you are mistress of that part of the bow, then do the same stroke, a little further down".
The détaché bow stroke is achieved by starting the stroke with a tiny little stroke of the bow, and then allowing the string to resonate. This is different from another French named bow stroke that is done on the string, called Martelé where the bow is hammered (hence the name) at the beginning and at the end of the stroke (rather like a hammer on an anvil) and that sounds more effortful.
The best way of developing the détaché stroke of articulation with the bow on the string, was described by Viotti, who was an Italian violinist of the late 18th Century, who then became the founding father of the French school. His method was to alternate up bows and down bows but blurring across the beat so that the bow stroke that fall on the naturally heavier beats of the bar alternates from up to down.
Whilst David plays that stroke, it's important for his whole arm to be involved in the work. He can then transfer that Viotti stroke to an ordinary détaché. If you watch carefully above you'll see even his upper arm is involved in tiny tiny soft movements that are part of the stroke.
During the 19th Century when the bulk of the repertoire that orchestras play today was written, the on the string style of articulation was that which was favoured by most composers and musicians (it was if you like the default articulation style).
Off the string articulation was thought of as not part of high art or high culture, but something for café fiddlers. Mendelssohn however (a little bit later) was famous for introducing the off the string style, particularly in scherzos, jokey music and character fairy music, such as his Midsummer Nights Dream. Apart from Mendelssohn's fairy music, on the string bowing was very much the norm during the 19th Century.
During the middle of the 20th Century, with the demand for string players to make more and more gramophone recordings the technique of playing off the string gradually rose into the ascendancy, this was mainly because it was easier to do and easier to get together.