Sour, where’d your freckles go?

@ColdhardSilver  

 
Well, it’s more, ‘dere’ stays the same because they’re always partly ‘dere dere’, an informal phrase that’s the Japanese equivalent of ‘lovey dovey’ (that’s kind of the point; They’re all weird ways to be lovey-dovey)  
‘Tsun Tsun’ is the equivalent phrase for when you turn away in anger.  
So, ‘Tsun Tsun’+‘Dere Dere’=Tsundere, meaning someone who is both lovey-dovey, and yet also pissed off. (“I didn’t d-do it for your s-sake, m-moron!” Blushes furiously)  
Yandere’s a bit different; It’s not ‘Yan Yan’ (whose meaning is entirely unrelated), but rather ‘Yanderu’(‘to be sick’) - so, a Yandere is someone who is lovey-dovey but also (mentally) sick, specifically used for violent insanity.
 
Sourdere is really just Tsundere but using ‘Sour’ instead to specify it’s the character.  
People do that all the time, though usually it’s part of the name being replaced with a word rather than the other way around; Silver Quill’s used ‘Flutterdry’, to give the first example I thought of.
 
Theoretically, ‘Yantsu’ could be a thing, but there’s less of a need for a word for characters acting angry in an violently insane way.  
Tsundere characters are ‘weird’ enough that a label for them is useful; Can’t really call them ‘lovey dovey’ without seeming to be inaccurate.

@Meso Echo  
TRUE

@621Chopsuey  
no dere
 
she is just bipolar

 
Sour Sweet is literally Akira Kogami. I kid you not.

@621Chopsuey  
More so tsundere.  
The “dere” comes from “dere dere” which means someone expressing their love and affection for their lover/potential lover.  
Tsun~~, yan~~, kuu~~, in this case sour~~, are all prefixes that explain the manner of which they go about expressing that love.  
Example: Thugdere: (s)he who expresses their affection through brutish or even illegal actions and other thug-based commonality; see example:  

Glasses aren’t just cute, They can also be sexy so it’s a good combo.

@StallingBV  
Seriously, she always looks cute.

@Collin Magney  
Yes, this is true

@621Chopsuey  
It’s for “tsundere” because she rapidly changes between flirty and angry. It doesn’t apply so much to this picture.

But Sour Sweet, you look really sexy with those glasses on.

@Appletank  
Yeah, I remember in the early ’00s when 2 or 3 girls I went to school with started wearing fake glasses. I guess it was a trend?

>“sourdere” tag
 
I’m new to the ‘dere’ terms. Is this yandere?

Either way I still love you babe.

@ChuymaruZ  

 
Blasphemy.

@Appletank  
Fake glasses can hurt your eyes, too. You still see the frame, or the glass, even if they aren’t prescription.

Check it  
You are pretty nice

Fake glasses do exist.

its ok, you are cuter without glasses

Needs less text.

My dear…you are cute no matter how you are. Angry or happy, its irrelevant. ;)