Tester I am sure I first heard used in the very early 1970's and I am sure its a blatant hint to drug testing. This term was first used as a snide comment (derogatory) to anyone who could go faster than you in a time trial inferring they were popping something. That's my understanding now commonly used to denote a time triallist.
Thats all for now. Keep those wheels spinning, in your memories if not still on the road. Be lucky Mick Butler Huntingdon UK.