Actually, this particular language is system-provided.
In my experience over the last month, when you add a new profile and don't put anything in the Source box (or something that is only three characters long), then when you hit the button to save the changes, the system will come back with the Source box in red and two check boxes next to it, with one saying "[[XXX]] will add sources by XXX (i.e., within 24 hours)" and the other saying "Unsourced Family tree handed down to [[XXX]]". When you check that box, that language gets added to the profile as a source.