The name of the device comes from the scientist who developed or best presented the functional principle(s) (see also: Occam's Razor, Schrödinger's Cat, Maxwell's Demon et alia). Fra Pelagatti is an Abbot of the Corbettite Monks.
From the description, it seems likely to function in a manner similar to an electromagnetic pulse, in which fluctuating fields interact with sensitive equipment to cause damaging current/voltage/energy surges. The "ætheric roar" provides a "static" which would disrupt local communications of a wireless or ætheric nature; the short bursts of dissonance would create the analogous waves which would provoke surges in reaction to the input energies.
Recently, after being apparently Agatha, it was revealed to have been preserved and possibly modified so that it shuts down the Castle temporarily rather than killing it outright. Agatha The Lion for this purpose when it attempts to prevent her from curing Gil, Tarvek and herself of Hogfarb's Resplendent Immolation.by
Possibly Relevant Outside InformationEdit
The title "Fra" refers to a friar or a monk. A similar title, "Fraa", receives extensive use in Neal Stephenson's recent novel, Anathem, which also deals with (mad) scientists sequestered in castles.