It’s been 23 years since the TV show Unsub came out. It was a show about the FBI starring that towhead from Starsky and Hutch.

Unsub is short for unknown subject of investigation. It means “the unidentified perpetrator”, basically.

When was the term actually coined?

It appears to be FBI jargon. I found a 1978 use in Google books (snippet view, but it looks like the date is correct).

Why a Congressional transcript would be limited to snippet view is beyond me. If anything is in the public domain, it’s the proceedings of Congress.

Thanks, Dave.

xxx