I've never heard the expression "folderol". I take it to mean "an idea of genius"...
folderol • n. 1 trivial or nonsensical fuss. 2 dated: a showy but useless item. ORIGIN from a meaningless refrain in old songs.
Folderol is a lovely phrase...I can picture Noel Coward saying it and giving that 'r' a leisurely, effortless roll...