Answer: lust is a word of German origin, it actually exists in German, still, although with slightly different meaning, and means ‘to want, to desire something’, without though implying ‘will’ (Wille), which is to say that it considers only the affective immediate wanting of something, usually linked to a physical need or to a physical apprehension of a lack of desire.
Passion comes from Greek ‘pathos’, which means to suffer, to endure, to support (ancient pathein) and is linked to love because it is supposed that love is imposed on mind, will and understanding, so that the self just ‘endures’ the effects of such an illness.
Love takes different turns depending on countries, nations, cultures and environments. I have always said that German knew so little about love that they had to take a Russian word in order to talk about: liubov (origin of the English love, too), as the original German is Minne.
Consequentky it is difficult to translate such words from one language to the other as they may imply completely different things. Thus ‘lust’ is frequently translated into French by ‘désir’, ‘désir sexuel’ and even ‘débauche’. But lust is not desire nor debauche as a debauche goes usually further than lust (implies even excessive drinking and eating, deviating sexual practices, among other – although it has lost much of its meaning nowadays and is used in order to imply disorder, chaotic situations, etc.), and desire has no negative implication, lust has.
Passion has changed slightly meaning as becoming a blind, almost desperate (I would say) longing for another that hardly considers the other’s point of view on the subject. In French ‘passion’ is more subtle, as it implies more a devotion than a blinding longing.
Lust has become the expression of sexual desire without implying anything else but a physical interaction, which though does not imply there is a deviating behaviour (as such, in number or frequency), just that a person becomes a sexual object for another, if there is a specified (not always the case), but just a fixation of attention on a certain number of practices without specification.
That the German almost ‘irresolute’ Lust becomes so sharply morally characterized in English is probably due to heavy Celtic, Greek and Latin (through Spain and France) influences, which escapes the German/German realm.
Meaning that the heavily defined words of Greek and Spanish create a ‘moral realm’ that finishes by pushing the original ‘Lust’ out of the moral spheres of the language, so that even the Russian ‘liubov’ regains its original meaning (lost in German, as Liebe has no moral implications whatsoever) to the point that it becomes as chaste as angels: love has as such no sexual implication whatsoever, … although it may.