The first component of the keyword is "01." To the uninitiated, this is merely a number. To the digital music enthusiast, it signifies the "Track Number" tag, a relic of the album-centric listening experience that defined the late 1990s and early 2000s.
: They released a collection of B-sides and rarities titled Judas O in 2001. 01 Judas m4a
The final and perhaps most technical component of the keyword is the file extension: . The first component of the keyword is "01