A hundred years ago, even in the US, men used last-name-only in addressing:
- Those of either sex who were distinctly inferior, socially or professionally
- Male equals with whom one was on familiar (but not necessarily intimate) terms
- Boys and young men to whom one stood in a professionally superior but socially equal relationship
They added the title in addressing:
- Social and professional superiors
- Social or professional inferiors of either sex entitled, by virtue of age or status, to a distinct mark of respect
- Male equals with whom one was not on familiar terms
- All women who were not distinctly inferior
One addressed by the first-name-only
- those of either sex with whom one was on affectionately intimate terms.
- children
- contemptibly remote inferiors
Women followed the same rules, with the sexes reversed, except that they addressed women equals by last-name-only only in (then rare) professional or school contexts, and the first-name "intimacy/familiarity" line seems to have been drawn a bit less stringently.
In the US, over the course of the last century, almost all uses have been swallowed up by first-name-only, except where tradition or professional discipline enforces use of titles to eminent superiors. I believe the same is coming-to-be in Great Britain, too; but you must consult a native speaker on that.
The use at Hogwarts in the Potter books reflects very traditional public-school practice, which spiceyokooko addresses in more detail in the Comments.
EDIT:
I am moved to add, in light of the discussion in the comments, that it would be gravely discourteous (not to mention deleterious to discipline) to omit a deserved title when addressing anyone in the presence of his or her subordinates.
How about moniker for the noun?
And I'd be inclined to invent monikerize for the verb.
(I also like appelation, but I don't have the right to up-vote it yet.)
Best Answer
The OED says "A hooded sweatshirt, fleece, or other garment.", and therein lies the answer, I think.
A hoodie is a "hooded sweatshirt" or "hooded fleece", (in contradistinction to the original kind of each, which had no hood) and the abbreviation is natural.
As far as I know "hooded coat" or "hooded raincoat" have never become established phrases, and so have not become "hoodies". This may be because on an outer garment (especially a raincoat) a hood is unremarkable, whereas on a sweatshirt it is much more distinctive; but that bit is speculation.