Board Thread:Speculation House/@comment-4957813-20140523184746/@comment-9090085-20140524043923

"Mercury" is most likely taken from the silvery liquid metal; note his color scheme.

While I don't really want to speculate too deeply, I assume the two are a "team", probably longtime partners. Which I mostly believe because of this comment on Emerald's page:

31.53.153.215: I did a bit of digging and according to hindu gem therapy, Emeralds are associated with the Planet Mercury, so it makes a bit more sense they are partnered with eachother. (I know, I just said he was named after the metal, not the planet; but this wouldn't be the first time RWBY has used multiple interpretations of the same aspect in-show)

As for their personalities, I'm going to make two assumptions:
 * 1 - some of the bad guys are deliberately designed to be the heroes' polar opposites in terms of behavior and fighting style.
 * 2 - Characters who are "paired" together generally have opposite traits(look at Ren and Nora to see what I mean).

With that in mind, looking at "party girl" Yang, I would imagine Mercury has an always serious demeanor to contrast her "have fun" personality.(Though just like how his weapons are mechanically similar to Yang's, just strapped to his feet instead of his arms, I wouldn't be surprised if he has a "berserk button" like Yang, just better hidden.)

Emerald is tricky, but I think she has a "laid back" attitude, to contrast her to both Mercury's "serious" and Weiss's "uptight" natures.

Her fighting style doesn't immediately com across as opposite Weiss's, But I'm guessing it's a little similar to Ruby and Cinder's "differences"(i.e., the person who calls her weapon "sweetheart" vs. the person who doesn't wield a weapon). So I imagine Weiss's single sword, with many "flashy" attacks, is opposed by Emerald's pair of "simple" pistols that turn into (stylized, chain-less) Kusarigama.

(now that I think about it, Emerald's weapons have more in common with Ren's Storm Flowers then most other weapons that have appeared so far)

Well that was long, full of wild guesswork, and went a bit off-topic. Feel free to punch it full of holes if you like.