"Who Dem" is dancehall song by Jamaican singer Capleton from his sixth studio album More Fire. It was voiced on Ward 21's Bellyas riddim and prior to the album, released on King Jammys label as seven inch single.
Arizona Cardinals wide receiver Larry Fitzgerald suggested, in a Twitter post to Chad Ochocinco, "Who Dem" as a nickname for the Cardinals football team following the lead of "Who Dat" (Saints) and "Who Dey" (Bengals).
References
Who Dem Wikipedia(Text) CC BY-SA