The alt-right usage etymology is ... convoluted, but dates to a gratuitously terrible film sequel ("Breakin' 2: Electric Boogaloo", 1984), and came to be a go-to reference for any sequel or return, here, with race war connotations:
https://knowyourmeme.com/memes/electric-boogaloo
Appropriation of language and symbology is quite common among similar movements.