X comes from Savage Mode, the 2016 collaborative project by Atlanta rapper 21 Savage and producer Metro Boomin, with a guest appearance from Future. The track became one of the breakout songs from the album and helped establish 21 Savage's deadpan style in mainstream trap. Short vocal cuts from the song later circulated on their own as reaction and flex sounds, detached from the full track. The money expandin phrase survived because it sums up the song's brag in a few seconds and works even without context.