I believe it comes from an old Roman word meaning 'young boy', although I could be wrong.
When I was a kid in Berwick, the word 'chavvy' was used instead of 'lad'.
( Davros' Granddad a voice of calm reason in a world of spastics., Fri 19 Jul 2013, 12:10, 2 replies, latest was 12 years ago)

I first heard charva about 15 years ago

( sporters I’m sincerely gratitude to you, Fri 19 Jul 2013, 12:11, Reply)

+y
From Oxford dictionary:
1990s: probably from Romany chavo 'boy, youth' or chavvy 'baby, child': sometimes said to have originated in Chatham, Kent, and to be a shortening of that name
( tangledupinblue hairy badge with moving eyes, Fri 19 Jul 2013, 12:12, Reply)

Wikipedia, that great font of accurancy, says:
The term has its origins in the Romani word chavi, meaning "child".
( Davros' Granddad a voice of calm reason in a world of spastics., Fri 19 Jul 2013, 12:14, Reply)