That's quite recent. I thought it had probably been around since the 1980s or early 1990s.
Children of the Sun RPG was the first publication to use the name Dieselpunk, back in 2001. The genre has been around for a while like Steampunk has before either were named.
Speaking of punk genres, I kinda like the name Trenchpunk for the Edwardian Era, don't know why, sounds cool.