If the product isn't directly competing, that is insane to call a common word or phrase intellectual property. Before you know it somebody will try to trademark taco tuesday.
And there are multiple live trademarks of Taco Tuesday in the US: http://tmsearch.uspto.gov/bin/showfield?f=toc&state=4803%3Ai...
In fact, in the field of Restaurant Services, two existing usages dating back to 1979 exist - one held by Taco John's everywhere except New Jersey[1] and one held by a hotel only in NJ[2].
And it looks like they're having a court case to see who truly owns Taco Tuesday®.
But none of those Taco Tuesday trademarks would prevent you from selling an app called Taco Tuesday that has nothing to do with food. Or start a clothing brand called Taco Tuesday. Etc. etc.
[1]: http://tmsearch.uspto.gov/bin/showfield?f=doc&state=4803:iid...
[2]: http://tmsearch.uspto.gov/bin/showfield?f=doc&state=4803:iid...