After a bit of searching, I managed to find the data structure that stores the name of your fortress. Trouble is, I can't trace that pointer back to a static address, so I can't write a tool for editing it. If you've got a memory editing tool (such as Cheat Engine), then it should be possible to change your fortress name that way - you'll need to figure out the word ID numbers for your current fortress name (by looking them up in language_words.txt - e.g. Releasetreaty -> 1541 [RELEASE] and 915 [TREATY]), then search for two consecutive 32-bit integers having those values (in this case, 0x00000605 and 0x00000393, giving the byte array "05 06 00 00 93 03 00 00"), then change those numbers to what you want your fortress to be called. Note that this won't change the parts of speech for the English translation, so if you replace a noun-only word with a verb-only word it'll display nothing (I don't recall how/where that info is defined). Also, if there are multiple instances of this, you'll probably want to change all of them in the same way.
This information is also stored in world.sav, but it's located at an unpredictable address (the fort's Dwarven name is stored as a string near the beginning, but that's only a cached copy that gets ignored once you actually load the world and overwritten once you save again).