How does one even create the title of an app when basically most nouns in the English language have been trademarked?
Related to: Trademark Infringement notice for usage of a dictionary word Jacuzzi in app - Google Play Store
You infringe a trademark when you use it in a way that allows confusion between your goods and services and their goods and services.
Trademarks are limited by geography (although global brands are ... global) and industry. You can use the word “apple” to sell, say, apples or plumbing services, but not computers or consumer electronics. You can also use the trademark Apple to identify goods and services made by Apple - because that’s what a trademark is for. You can’t use it in a way that people could be confused that your goods and services are their goods and services or are related to or endorsed by them.
Trademark infringement occurs when you use a trademark name in a way that confuses consumers about the source of some goods or services. If you use a word that happens to be a trademark in a context completely outside the context of the mark as an identifier for a business, there's no infringement. Just because "Apple" is a trademark for a brand of computers does not preclude you from talking about pieces of fruit called apples.
Trademarks are also domain-specific, so a landscaping service and a restaurant might have the same trademarked name with no issue: there's no possibility of confusing the two businesses, despite their identical name. However, trademarks found to be "famous" in some jurisdictions enjoy a cross-domain trademark monopoly: you cannot, for example, sell bicycles under the famous name "Coca-cola" despite your bike business having no relation to the soft drink industry.
Outside of "Jacuzzi" as a trademark, the word only has signifance as a person's name. (It is named after the company's founders.) Since your product has no association with any person named Jacuzzi, but does appear to be associated with hot tubs, the potential for confusion is abundant. Your use of the Jacuzzi name in association with a hot-tub-related app clearly associates itself with the Jacuzzi Brands company without authorization.
It is possible for a trademark to succumb to "genericide" whereby the legal status of a trademark is lost due to widespread use of the mark to signify a generic category of products, rather than a specific producer of a product. For example, "aspirin" and "escalator" used to be trademark names, but now are no longer protected as trademarks. It is exactly out of fear of genericide that companies like Jacuzzi aggressively litigate generic misuse of their brand names.
I’d offer another example regarding confusion. McDonald’s is a well-known fast food restaurant. There have been cases of family restaurants that had this name being forced to change it, as the business was similar, i.e. selling food.
I doubt the restaurant would have any claim against McDonald’s Custom Crafted Furniture.
And on a side note, Pandora the music service lives a happy coexistence with Pandora the jewelry store. I was about to extend the joke regarding custom furniture, when a quick search led me to a “Pandora Reclining Sofa.” Proving the point that there seems to be no confusion leading to court between these companies.
Lest I leave before addressing the Apple in the room - Apple Records was the Beatles’ record label, and fought hard against Steve Jobs naming Apple. The defense brought to the courts was that a computer company wasn’t going into the music business. The rest is history.
