Aussie VC 67 Dodge ute
trimmer is short for "motorbody and coach trimmer" as the old full name for the trade...or "motor trimmer" as it's known now, most people just call us car upholsterers!!
I'm on a trade forum in the US...they refer to themselves as "auto trimmers" it's not a trade that many would know the correct title for!!
had a quick look at your build thread...haven't been there for a while, how's the progress