Parallel of Origin
I had never heard of "parallels of origin" either. Apparently for a Lambert's conical chart, the 'parallels of origin' are midway between the standard parallels. And although great circles are approximately a straight line on a Lambert's, they are actually 'concave to the parallel of origin'. If this is drawn in the exam question I was given, the great circle almost appears as an "S" shape when it passes through the origin.
It seems like unnecessary detail...