Right I should probably explain who onionElsa really is. onionElsa is basically one of the early character designs of Elsa. I’m not entirely sure of the exact time table, but in one of the earlier drafts of Frozen, Elsa was written as a redeemable villain. Pic related is what she looked like while she was still this redeemable villain character. In fact if you’ve ever seen that early animation teaser (the one where Anna says “that’s no blizzard, that’s my sister) you can catch a glimpse of Elsa in the onionElsa model form.

Now of course there was many different versions of the design, but the basic characteristics of onionElsa is short hair that’s spiked up in the back, unkempt bangs, and usually a villainous or devious demeanor. Her hair color ranged from blue to black to platinum blonde (and judging from that teaser, I think the final design was blonde). Black and platinum blonde are most common in fanart though, because the blue hair is usually associated with the blue-skinned concept art of Elsa.

There isn’t really a single name to call her because she is just Elsa. Usually people call her evilElsa, earlyElsa, or conceptElsa here on tumblr. I call her onionElsa to make it simple. The name onionElsa actually first appeared in January on 4chan’s /co/. I didn’t make it up personally, but I picked it up when people started calling her that because her hair reminded people of an onion. Ducktail!Elsa was also suggested at the time, because her hair also looks like a the tail of a duck, but that didn’t catch on.

Typically in fics and fanart, onionElsa is portrayed as either a more villainous or confident version of Elsa. Sometimes onionElsa replaces Elsa as a character and sometimes she’s her own separate character besides Elsa with her own real name (for example in my fic she’s Elsa’s twin named Elise). Usually in the latter cases, onionElsa is either a alternate reality version of Elsa or Elsa’s twin/sister. Of course she’s not always portrayed as a villain character, in fact I’d say onionElsa is less portrayed as a villain than she is portrayed as a villain and it’s usually in fanart than in fics.

Also note, evil!Elsa and dark!Elsa do not always equal onionElsa. Sometimes evil!Elsa and dark!Elsa can be referring to the final form of Elsa that we all know and love gone evil.

I hoped this wall of text cleared things up.

Edit: These concept art pictures are from the Art of Frozen book.

Double Edit: It was January, not December when the name onionElsa first appeared. Though there were references of her head looking like an onion as early as late December.