Linda said:
It sounds to me like it's saying that the idea came from Edward Irving. Or am I reading blond again?

From the Wikipedia article:

Margaret was a member of Edward Irving's congregation and shared with him her visions of a secret rapture of the church.

She also shared these same views with John Darby during a Darby visit of Port Glasgow.

Irving proposed the new doctrine of a secret rapture of the church (from Margaret McDonald's visions) at a prophecy conference ...and soon after, Darby developed the full-fledged doctrine of Dispensationalism.

Synopsis

Margaret had a vision about a secret rapture.

She told her preacher, Ed.

Ed began to teach it as doctrine.

Both Margaret and Ed influenced Darby.

Darby incorporated the "secret rapture" doctrube into his new leaven called "Dispensationalism".

Margaret McDonald's prophecy was the source where the original idea of a secret rapture came from.

Ed Irving and John Darby developed it into a doctrine.