Now some scientists have learned something interesting via ancient DNA:
Based on the genetic analysis of two members of the Árpád Dynasty, it appears that they derived from a lineage (R-Z2125) that is currently predominantly present among ethnic groups (Pashtun, Tadjik, Turkmen, Uzbek, and Bashkir) speaking Iranian or Turkic languages.
One of the Arpads they sampled was King Béla III (1172–1196); the other was one of additional individuals (six males, two females) who were also placed in the Royal Basilica of Székesfehérvár.
So the male founder of the Arpad line really did come from central Asia into Europe, which means that for all we know the dynasty really was descended from Attila.
But rather than coats of arms the Polish nobility liked to identify their families using abstract signs called Tamga. There's one in the plaque above, surrounded by winged Victories. Modern archaeology shows that these were once widely used across the steppes and into central Asia, especially by the Sarmatians. Not, so far as we know, by the Slavs. Archaeology also shows that people who were probably Alans, a Sarmatian offshoot, did settle in southern Poland in the post-Roman age of migrations.
Sometimes weird old legends have some truth to them.