In german the distinction between a "Messer" (=knife) and a "Dagger" (=Dolch) is defined by the number of edges of the blade: anything with a single edge is called a "Messer", all double edged blades are a "Dolch" (=dagger). Nevertheless, a single edged rondel dagger will still be called a "ScheibenDOLCH", for the same reasons you mentioned: it is made for fighting and in this case it is defined by its purpose.
in Germany and Austria, there were different guilds for knife makers and sword makers. You were only allowed to produce products that are covered by the regulations of your guild. A sword (or dagger) was made by: Bladesmith (ger: Klingenschmied), Hiltmaker (ger: Gehilzmacher), Sharpener and polisher (ger: Schwertfeger). A knife was made by: the knifemaker (ger: Messerer). So boiled down to the essence, a knife was cheaper, because you only had to pay one person and not three, also you only paid guild fees one time and not three times.
Like many have said, daggers generally have a double edged blade. Many legal codes in the US distinguish Daggers (double-edged) and Dirks (single-edge) from knives (single-edge). I'm going to say that while most daggers, dirks and knives follow this convention, not all. I've never see a Bowie knife described as a dagger or dirk, but in most cases they are very clearly intended for fighting. Historically, some States, Territories, Cities banned the carry of Bowie knives, just as many still ban daggers and dirks (and Balisong/"Butterfly knives"). I'll add that I agree, daggers and dirks are primarily intended for stabbing, not cutting.
Busca el canal Antiguo Acero Español. Explica la diferencia. Puñal son armas pequeñas utilizadas para apuñalar. Daga se utilizaba en conjunto con la espada y tamaño de la Daga es 1/3 el tamaño de la espada. Hoy en día se ha perdido el término puñal y se usa principalmente daga de forma incorrecta para referirse a lo que es un puñal. Básicamente todas las "dagas" modernas tácticas como el Fairbairn Sykes, el Gerber Mk II son puñales.
There is a lot of historical context for why the English didnt like people eating w/ weapons. There is historical context for people being slaughtered while they eat & make merry we will say. Lol