The reason, Ashigara was called hungry wolf was because when the British compared her with the other cruisers present at the Naval Review, she was smaller and thinner, it was actually an insult but the Japanese interpreted as a compliment and the nickname stuck

Kind of how the B-17 got the name "Flying Fortress" though that was an actual compliment

…and I always thought Flying Fortress is a name made by Boeing’s marketing department for their pitch to the DoD and public

Seika said:

…and I always thought Flying Fortress is a name made by Boeing’s marketing department for their pitch to the DoD and public

I think the name "Flying Fortress" was actually came from the pilots and it's crew due to it's durability and... Lots of Machine Guns.

The "flying fortress" name apparently originated in 1935 from the Seattle Times's Richard Williams, describing what was then the Boeing 299.

I'm usually skeptical of Wikipedia attributions on this sort of thing, but a 1989 Los Angeles Times death notice for Williams says the same.