The name of an app in a Google Play app listing is called the app title, and plays a big role in how Google indexes an app for appearing in search results. Other components of a Google Play app store listing that impact how an app ranks and for which app store searches include the short description and the full description. 
Google Play app name length
It is generally recognized that the less space in a field, the greater the importance (or weight) given to the field. Like a pyramid with the Google Play app name at the top. For example, Google provides only 30 characters (spaces included) for the app title, with the words used in the app title carrying more weight than either short or long description fields (which have 80 and 4,000 characters respectively). Not only are the words used in the Google Play app title important for indexing, the App Title also tells the user in a few seconds what you app does. Because the title of an app impacts both discovery and conversion - an optimized title maybe the most critical piece of an ASO strategy.
An optimized Google Play app name
An optimized app title starts with understanding which features of an app are most in-demand or differentiating, and how the market is referring to these features.
recommends “brand name + key function”. For Google Play ASO purposes, format the app title using the app name and the most important relevant feature (or function). Google Play ASO is much more about relevance then trying to rank for words or phrases that have a lot of search traffic. Because conversion from search impacts what an app is ranked for, targeting relevant features (keywords and phrases) produces a far better result than aiming too broadly.
App Name Examples
A good
example of an app title that makes good use of the 30 characters is
hotels.com. 
App Name Guidelines
From time to time, Google updates the guidelines and restrictions to app names in Google Play. The most common restriction to avoid is creating an app name with another's brand in the beginning or start of the app title. 