Green’s Dictionary of Slang

(orig. US) a simple piece of graffiti art, using only two colours, e.g. the artist’s own name.

1982		C. Castleman Getting Up: Subway Graffiti In N.Y. 31: The term throw-up is also used to refer to writing done in other forms that is lacking in style. When used to describe anything but an intentional throw-up, the term has the same meaning as bad style.
2001		James Cook University (Aus.) 🌐 Beginner artists develop their own personalised ‘tag’, while a slightly more developed form of art is known as a ‘throw-up.’.
2004		Taskforce ‘Still Bombing’ 🎵 I leave a full throw-up on your street-sign.
2014		A. Fox-Lerner ‘Traces of a Name’ in ThugLit Mar. [ebook] He picked shit with me because he claimed I was targeting his tags with my throw-ups.