Green’s Dictionary of Slang

on (pirate) radio stations, to send a greeting or acknowledgement to a named listener or group of listeners.

1997–2000		Da Bomb 🌐 25: Shout out: To call; or to say hello. Give a shout out to Mike for me.
2001		N. Macdonald Graffiti Subculture xii: Shout out: To thank or acknowledge someone.
2002		Teen Lingo: The Source for Youth Ministry 🌐 shout out accolades, recognition.
2005		B. Coleman Rakim Told Me 186: ‘I shout out DJ Speed there on ["Let the Bass Go’], he ended up being my DJ’.