I had a browse through the British Newspaper Archives, and there are a handful of articles which include the name “Onanoff” Johnson, together with one which refers to him as David “On and off” Johnson, leading Middlesbrough star and their most daredevil rider, who had completed the speedway season unscathed, only to badly break his leg playing football.
I noted other nicknames in the few articles I found…
Riskit Riley
Broadside Burton
Skid Skinner - which reminded me of Skid Pitcher!
Smoky Stratton
Dare-devil Beckett
Broncho Dixon
and a couple of more well-known ones…
Sprouts Elder (James Lloyd Elder)
Buster Frogley (Arthur Robert Frogley)