Schweinshaxe is the traditional name in Germany. Elsewhere, butchers sell the same piece — or a close cousin — under a different name.
Both pork hock preparations from European tradition — Schweinshaxe is German-Bavarian roasted-with-crackling, jambonneau is French cured-and-cooked. Same anatomy, different traditions.
Same anatomical cut (the lower-leg/hock joint). Schweinshaxe is specifically the Bavarian roasted preparation with crackling skin; the generic 'pork knuckle' covers boiled, cured, smoked, and pickled preparations across other traditions.