grammar - Is there a term for the use of adjectives as nouns?

I wonder when this horrible trend started—to me it seems to have proliferated very recently, over the last year or two:

Give the gift of happy this Christmas

..or how about this, from the website of a taxi-hailing smartphone app:

Quick, safe and reliable is right at your fingertips.

Ignoring for the moment the equally mind-boggling choice of is rather than are in that sentence, is there term for this marketing-led practice of using adjectives as abstract nouns? (By "term" I mean a noun—I can think of many adjectives to describe it.)

Edit: I see this as somewhat distinct from the use of adjectives as concrete countable nouns, to which I'd become more accustomed without even noticing it. Usually it's when "one" or "ones" or "thing" or "things" is implicit, as in The Incredibles, or The Good, The Bad And The Ugly, or you have to take the rough with the smooth. To me, somehow, the definite article makes it OK, whereas it's a whole new level of nasty (sic) to use adjectives as abstract uncountable nouns. Maybe there's a lot of subjectivity in that.

Edit 2: Maybe the defining difference between these new formations and other more-established zero-derivation nominalizations (thank you tchrist for the terms) is this: in the older cases they tend to be a good way of expressing an idea more succinctly than otherwise (try rewriting you've got to take the rough with the smooth and it will sound less pithy); by contrast, in the offending new cases there is already a perfectly good abstract noun that would fit right into the sentence without changing the meaning (happiness, speed, safety and reliability in the above examples).

Answer

This is nominalization produced by zero derivation. That happens when a non-noun is used as a noun without requiring that some derivational affix be applied to do so.

Per Wikipedia:

In linguistics, nominalization or nominalisation is the use of a word which is not a noun (e.g. a verb, an adjective or an adverb) as a noun, or as the head of a noun phrase, with or without morphological transformation.

[...]

Some languages simply allow verbs to be used as nouns without inflectional difference (conversion or zero derivation), while others require some form of morphological transformation. English has cases of both.

This in particular is zero derivation, which again per Wikipedia is:

In linguistics, conversion, also called zero derivation, is a kind of word formation; specifically, it is the creation of a word (of a new word class) from an existing word (of a different word class) without any change in form. For example, the noun green in golf (referring to a putting-green) is derived ultimately from the adjective green.

Conversions from adjectives to nouns and vice versa are both very common and unnotable in English; much more remarked upon is the creation of a verb by converting a noun or other word (e.g., the adjective clean becomes the verb to clean).

In other words, this happens constantly and is wholly unremarkable.