What meaning is "legitimate(ly)" gaining?

I'm familiar with the following meanings of legitimately

In a way that conforms to the law or to rules

and

In a way that can be defended with logic or justification; fairly

(both from ODO)

But recently I have seen legitimately and legitimate used to mean something else. I can't tell if it's just an intensifier, like very (adv) or extreme (adj) or if it's being mistaken for another word, or what.

Below are some examples. Can someone pinpoint this emerging meaning?

TIL some children have such a legitimate fear of math that brain scans actually show their amygdalae (fear centers) activate when faced with a math problem.

(reddit)

This isn't using legitimate to mean a fear that conforms to rules, nor is justifiable, because neither of those things would affect how it shows up in a brain scan. The strength of the fear would affect that.

I look like I'm legitimately scared of food.

(BuzzFeed)

This isn't about legality or justifiability because that cannot be conveyed by a look.

I legitimately think whoever designed Yeezys did it for a bet. "I bet you can't design the worlds ugliest shoe and sell it for $2,000."

(Clint Evans, twitter)

This isn't about legality because we don't have thought police. It could be about justifiability, but semantically is seems more likely to mean honestly or really.

While the uses are different, they seem to be converging to a similar meaning. I just can't quite figure out what it is.

Solution 1:

Legitimate in your examples means real or genuine.

The example I have linked to is:

It's not clear that the letter is legitimate [=genuine]; it may be a forgery.

This shows the meaning works well with your examples, where people might question the authenticity of the person's action or feeling.

Solution 2:

I would postulate that legitimately in these contexts arises from an extrapolation of the concept of legitimacy in a political context. To summarize Wikipedia's entry, political legitimacy is the recognition of some kind of authority.

In this sense, legitimately is used to express the authoritative truthiness of the statement, so it is closer to actual than it is to very or extremely. You could substitute real or actual into your sentences and they would convey the same meaning.

Solution 3:

I consider the colloquial meanings of ‘legitimate’ and ‘legitimately’ cited by the OP to be a mix between objective/ly and justifiable.

1. TIL some children have such a fear of math, in the objective sense, that brain scans actually show their amygdalae (fear centers) activate when faced with a math problem
   (the ‘fear of math’ is real/objective, and it is ‘legitimized’/supported by science).
2. When seen objectively, I am scared of food (this is an objective assessment of the facts).
3. Objectively speaking, I think whoever designed Yeezys did it for a bet ... (it is an objective/impartial standpoint).

_{^{TIL=today I learned}}

Solution 4:

Your first guess is basically correct, the meaning here of legitimately can be compared to the meanings of very or extremely. As you might guess from the term's more formal meaning, definitely or surely are sometimes a little closer to what the writer is trying to express.

The reason you aren't likely to find this usage in dictionaries is because it is colloquial. There is an even more colloquial version: "legit". That abbreviation is very colloquial, mostly only used by young adults, and never used in formal situations (unless one is trying to make a bad impression).

Using legitimately in such a way won't be looked down upon nearly so much as legit but it's still a manner of speech best avoided. Understand what it means but please don't use it yourself.

I fear there is some danger here of overthinking this. When interpreting colloquial speech you could assume the word legitimate to mean "logically defensible" and the given sentence will probably make sense. But in most cases the writer really only meant "extremely" or something similar. As always, a word that has several possible meanings is colored in by its context.

I'm somewhat conflicted by the first example (TIL some children have...) as I look at it more. As for the guy who is "legitimately scared of food", the overall context suggests that he probably just means "extremely scared of food" and didn't intend to imply that he could logically defend his fear of food.