[mandatory I Am Not A Lawyer prefix]
Do not overthink this - using a part of the Stack Exchange trademark, especially if it occurs naturally in the name of your app, is perfectly fine (unless you are trying to make a competitor service and then register it as a trademark yourself - this might get a bit more complicated).
The important part of the quote you provided is not the example, it is this part:
Do name your application with something unique.
There are numerous prominent user organizations, applications, and scripts that are using the trademark even in full (the Stack Overflow one) - however, they are called sufficiently uniquely to be absolutely in the clear:
- SOCVR (Stack Overflow Close Vote Reviewers)
- SOX (Stack Overflow Extras)
- SOUP (The Stack Overflow Unofficial Patch)
The list goes on. Some of the above explicitly add a note that they are not affiliated with Stack Exchange (e.g. SOBotic's "We are not affiliated with Stack Overflow or the Stack Exchange Network."), though.