Fanon

Definition

Facts about a fandom or fictional universe that hasn't been confirmed by the creator but the fandom generally accepts as fact.

More widely accepted than headcanons and once confirmed is capable of becoming canon.

In fanfiction Shinichi Kudo always, always drinks his coffee black. Some go further to say that he is a coffee addict. This could've been sourced from Sherlock Holmes, who was a cocaine and morphine addict.