Is there a term for using “or” to introduce something like an appositive?

Question

Recently someone was trying to explain to me that "or" can have a non-disjunctive function, and this came to mind as a possible example but I can't figure out the terminology to describe it. I know that I've seen "or" used to introduce something like an appositive in a sentence, thusly:

"In her 'vlog,' or video log, she asserted that..."

Actually, now I'm not totally sure that's really an appositive. Anyway, I'm not finding this under anything I have on "or" or appositives, so I'm wondering if it's a legitimate usage with a name, a weird colloquialism, or what.

Also, potentially, from "Sixteen Going on Seventeen" from The Sound of Music: "...sometime in my youth, or childhood/I must have done something good" (depending upon whether "youth" and "childhood" are the same thing in this song).

Answer 1

There doesn't seem to be a uniformly accepted name for these, so I'll summarize what two leading comprehensive grammars of English have to say about it.

ComGEL (Quirk et al.)

ComGEL would call or video log a strict nonrestrictive apposition, where or is an explicit indicator of apposition (pp. 1307-1313). In appositions, ComGEL recognizes a semantic scale running from equivalence (i.e. 'most appositive') to loose and unequal relationship ('least appositive'), such as exemplification. Or is used when equivalence is meant, in particular appellation (though in this context it is not used as frequently as some other explicit markers, such as namely, that is to say, and in other words) and reformulation.

CGEL (Huddleston and Pullum)

CGEL refers to such things as supplements whose form is that of clauses and phrases introduced by a coordinator (pp. 1361-1362). Specifically, about those introduced by or, CGEL says (p. 1362)

Supplements introduced by or are used to express reformulations or corrections:

[34]  i  I'm convinced it was masterminded by Tom—or Ginger, as everyone calls him.
         ii  They'll be finishing on Tuesday—or at least that's what they said.

Elsewhere in CGEL it is made clear that supplements may be introduced in many ways, including by commas, parentheses, and dashes (p. 1350):

In speech, supplements are marked as such by the prosody: they are intonationally separate from the rest of the sentence. In writing, they are normally set off from the rest of the sentence by punctuation marks—commas, or stronger marks such as dashes, parentheses, or (in the cases of appendages in end position) a colon. Punctuation allows for different degrees of separation, as described in Ch. 20, §§4-5.

About dashes

The kind of dash or dashes to be used is a matter of style. For example, the Chicago Manual of Style recommends em dashes for this purpose, but notes that

In British usage, an en dash (with space before and after) is usually preferred to the em dash as punctuation in running text, a practice that is followed by some non-British publications as well.