Please answer a question about the following article about House music:

Rachel Cain, co-founder of an influential Trax Records, was previously involved in the burgeoning punk scene and cites industrial and post-punk record store Wax Trax! Records as an important connection between the ever-changing underground sounds of Chicago. As most proto-house DJs were primarily stuck to playing their conventional ensemble of dance records, Frankie Knuckles and Ron Hardy, two influential pioneers of house music, were known for their out-of-bounds behavior. The former, credited as "the Godfather of House," worked primarily with early disco music with a hint of new and different music (whether it was post-punk or post-disco) but still enjoying a variety of music, while the latter produced unconventional DIY mixtapes which he later played straight-on in the music club Muzic Box, boiling with raw energy. Marshall Jefferson, who would later appear with the Chicago house classic "Move Your Body (The House-Music Anthem)," (originally released on Chicago-based Trax Records) got involved in house music after hearing Ron Hardy's music in Muzic Box.

what was the nickname of frankie knuckles?
"the Godfather of House,"