How ‘HOW’ change the meaning of the Twinkle song?

I'm a Spanish speaker so this makes me confused. In the song, Twinkle, Twinkle, Little Star

I would understand

I wonder what you are! ==> Me pregunto que eres (seras)!

But they add HOW before. And I can't find something similar to translate to.

How I wonder what you are!

Google translator doesn't make sense to me:

¡Cómo me pregunto lo que eres!

With these two it doesn't have any problem.

Are you sure? ==> Esta usted seguro?
How are you sure? ==> Como esta usted seguro?

So what is the meaning of that sentence?
Is wondering how become what is now?

Solution 1:

Adding to @HotLick's great answer, the adverb how (See No. 3 definition) can be used as a modifier to

indicate surprise, delight, or other strong feelings.

[Wiktionary]

It has two usages as follows:

1. It modifies other adjectives or adverbs as in

How very interesting!

How wonderful it was to receive your invitation.‎

How seldom I go there!

2. It modifies the entire sentence as in:

How it rains! (It rains a lot.)

How I envy you! (I envy you a lot.)

How I wish to go to Paris! (I really want to go to Paris, but I can't.)

How do you like that! (You seem to like that a lot. I am surprised.)

"How I wonder what you are!" means "I wonder what you are a lot (or very often)."

Solution 2:

It's a modifier to express surprise or strength of meaning.

To put this in context, the "how" works much in the same way that you, as a Spanish speaker, might exclaim "qué fuerte!" instead of just "fuerte!".

Solution 3:

Two ways of considering it.

One view would be that "how" is used as a simple intensifier -- "I wonder greatly what you are". (This would be the most common understanding, as "how" is often used for such effect.)

The other view would be that "how" implies a sort of "meta wonder" -- "Wondering about your nature is thought provoking".

Of course, since most people learn the song at a very early age they never consider the possibility of such deeper meanings. And, as TrevorD notes, the word is at least partly employed to fill out the meter of the rhyme.