I would think the first sign would be a cease and desist / Abmahnung Yo or more specifically Yo! has been trademarked in many countries since the mid-90's as p

I would think the first sign would be a cease and desist / Abmahnung Yo or more specifically Yo! has been trademarked in many countries since the mid-90's as part of the Yo! Sushi brand. It depends on what you are building towards. Are you getting revenue from the app? If you were to have to pull the app from the store is that your whole business gone?