That's a simple question to answer about why Soma named it Diesel - cos it would sell a lot of buds in the coffeeshops and seeds for himself, Diesel is a name many US folks will crave but Grapefruit isn't.
I remember a session with hazyfontazy and THC4Sim earlier this year where we were caning the ECSD, Cheese and NYCD and my comments on the ECSD was 'If I'd found this plant I'd have called it red evostik (after the glue) cos it has a very solvent/glue quality about it and smelt like red evostik to me. At the same time I said I'd have called Cheese 'dusty sweaty feet' cops that's what it smells liek to me - sweaty feet with that dry dusty smell as well.
There are cuts named after how they smell - dogshit for example, but in this day and age, folks give things names like Diesel, Kush, or Chem or Dawg cos it's all about the names, not the genes, blame the 50+ years of marketing and advertising for turning us into a culture that satiates over brandnames.
Sonic, Subcool and I have all said recently that we are highly sick of this and joked that we would like to be able to call things names like 'sativa #1' or 'good shit #1'.