Bergholt had never actually wanted to be an engineer, he knew even at a young age that it wasn't really the career path meant for him. He'd only gone to the Engineer's Guild school because of his Legacy Scholarship. His mother had been a genius when it came to bridge supports. Not that anyone took notice of the person who designed the bridge supports, no they all paid attention to the person who was in charge of the project and who came up with the idea for the bridge and ignored the other half-dozen engineers that worked on building the thing. His mother had gone unnoticed and without acclaim by everyone but the Engineer's Guild. There she had been celebrated and because of that Bergholt wasn't kicked out when it became clear that he had the exact opposite of talent when it came to designing things.
On Parent's Night his teachers would talk about his creativity and prowess with numbers without ever actually going into details about what either of those brought about. His mother had gone to her grave thinking that he would give the Johnson name the acclaim she never managed; and while he certainly gave it acclaim, he's pretty sure it's not the acclaim she wanted. It was probably for the best that she didn't live long enough to see her son turn the name Johnson into a synonym for bad engineering.
In later years it would always amaze him that one night out at the bar would change his life. It had been a simple mistake, just one of the usual tricks engineers played to get free drinks, only somehow, Bergholt had managed to turn the three-toothpicks trick into something that catapulted the little ball across the bar and through the main window. It wasn't the first time he'd done something like that, he'd been banned from practical experimentation years ago by the Guild, but they were all drunk and his friends forgot how badly things could go wrong. It would've gone down as just another bizarre thing Bergholt had done, laughed about the next day as they finished up classes in preparation of graduation, if the noble hadn't been there.
A lord who had stopped in for "a cup with the common people" and seen what Bergholt had created. He'd offered Bergholt a job right there, complete with a rather sizable commission, and wouldn't take no for an answer. Not that Bergholt would've said no, he had no prospects once his schooling was completed and anything to help him get by was going to be a good thing. It wasn't until later that he realized his benefactor was expecting him to develop a new, more portable, trebuchet. One that could perhaps be wheeled conveniently down the streets of Ankh-Morpork for inter-family conflicts. He'd done his best, he really had, but the end result had been something that ended up digging really neat holes, about a meter deep, and only flinging stones by accident when it was going through cobblestone.
Some landscapers who could see a future free of digging holes for large plants and trees happily paid him for the machine, enough to re-pay the cost of building it and still allow him to live for a week, so it wasn't a complete loss. That would've been the end of it if some other nobleman hadn't given him a bunch of gold to build a new carriage house. The resulting building wasn't much good for carriages, but it did worked splendidly for geese and cats. Regardless the nobleman didn't ask for any money back because he'd hired Bergholt more to see what would be produced than because he wanted anything specific. That was the start of it.
Before long he was in high demand, everyone from his neighbors to the Patrician was trying to hire him. Sometimes even given money just to use on "whatever" because the clients wanted to see just what he'd come up with (he tended to do pipe organs on those occasions, he always liked music). Everyone in the city wanted a Johnson for their very own. It was depressing.
He didn't know why everything he designed ended up the way it did (and no amount of apologizing to the Archchancellor would ever make him comfortable being in the same room as a wizard ever again). He'd have loved to be able to create things that people actually wanted, rather than things that people merely wanted to see what they'd end up doing. He had hoped that he would some day find a way to make his mother proud of him, instead he could only be gratefully she hadn't decided to become a zombie.
He liked to think she would have approved of what he did with the money though as his work did allow for a sizable scholarship fund. In the future the Guild would be able to find children with promise and train them up into good engineers, people worthy of the title. And perhaps the Emiglia Fairten Johnson Memorial Fund would make up for Bloody Stupid Johnson.