Interesting. i had remained with Gallez saying that the tribe of Quraish was mentionned in the 5th/6th century but he did again what he does best, meaning twisting words to fit his rationale.
Of course, Gallez does this very well, but not always and this is the case here.
It is more complicated, Morris does not tell all the story:
In 1905, in his book Narsaï doctoris Syri homiliae et carmina primo edita (vol. I, pp. 115-116 and 117, published in Mosul), Mingana had first mentioned "Qadishaye", but it was a false reading, he explains at the bottom of page XIII, note 1: "as the manuscript requires", it should read qršy' and not qdšy' (the difference lies in the situation of the point compared with the letter).