Whether stainless or carbon (or ceramic), you should clean your knife as you work. Doing so will prevent it from rusting and build a patina (if carbon) which will further help prevent rust.
If you want to force the patina, this video by Knifewear might help.
Sharp Knife Shop has a good video about patinas.
I’m not sure when PB&Js became less awkward but the first recipe for PB&J appeared in 1901 and called for currant or crab apple jelly.
National Peanut Butter Board
Turns out Tasting History has a fun video on this topic.