An insult that became popular in the 80's, meaning an idiot. Scholars of urban
slang have long believed this word originated at Woodstock (15-17th Aug'69), when some
hippy lost his
dog called Wally. He wandered around the site shouting Wally, and before long the crowd started shouting it. After that, wally became a popular chant at
music festivals. However, on a recording of a Jimi Hendrix concert on 9th Jan 1969 in
Sweden (7 months before Woodstock), someone in the audience shouts wally while Jimi is dedicating a song, prompting him to say "yeah, this song is for wally too". So, while the word probably did originate at a festival, if has to be another one, not Woodstock.