Spring environment variable not correctly read into property

Question

This question is not about escaping characters such as = or " in the property. The questions are:

1. How do I get the expected values, e.g. for the password I want DE#F and not DE
2. More academically; why is this happening?

(I assume) Spring is not reading in the environment variables correctly that contains an # in the string - on Linux. E.g.:

The yml file:

# Spring Boot configuration in yml file
application:
    username: Clark Kent
    password: abc

The overriding environmental variable in /etc/environment

APPLICATION_USERNAME="Ronald Raygan" #Maybe use a stronger password?
APPLICATION_PASSWORD="DE#F"

In the application, the following values are used:

@ConfigurationProperties(prefix = "application", ignoreUnknownFields = false)
public class ApplicationProperties {    
    private String username;
    private String password;
    // rest of the class
}

In another class:

System.out.println(applicationProperties.getUsername());
System.out.println(applicationProperties.getPassword());

This will print out:

Ronald Raygan"
DE