I don't have a name for my skid - but we call BM "The PEW" (Psycho Ex-Wife).

We pretty much ONLY call her that.  Never use her name.

I also have no nickname for my SD but we call BM the Yeti or the Skag. Both names are a dig at the fact that she always smells like rotten BO and  stale cigarette smoke.

I have to say I saw someone years ago and on another site but thought is was perfect.  For years we have referred to her as CP.  it’s come in handy for discussing things if the kids were at the house so we didn’t ID their mom.  

It’s tons better than Satan, which is what my DH used to refer to her as.  Even Satan isn’t as much of a d1ck as she is, it takes away power and turns her more into what she is - someone with some sort of mental imbalance that she’s not addressing.

It's an acronym to reflect her "f"ace and "w"hore-ish-ness (the "C" word doesn't get said much, but it's in the acronym!).  The skids have no idea what it is when we slip up, which is awesome.

Her name is Crea and my now 9 year old thought we were saying Korea when we speak about her. And then we thought well she is like a tyrannical communist dictator country hell bent in nuclear war so   It was a natural nickname . I had to clean out their marital home when the house was sold and I found all of her old memberolia and letters from high school and her 20's and I discovered it was not a new nickname to her. I refer to my stepkids as the Kardashians but ironically enough my daughter's father named our daughter and she has  Kardashian name and so do I. ):

.......on our mood

'Hyacinth' - Named in honour of a character from a Britsh sitcom about a snobbish lower middle class social climber, Hyacinth Bucket (who insists that her surname is pronounced “Bouquet") The sitcom follows Hyacinth in her attempts to prove her social superiority, and to gain standing with those she considers upper class.

'Labrat' - Because she just keeps trying to push DH's buttons, even though she never gets a 'treat' (his attention) anymore

'That thing over the water' (husband is Scottish so said with a Scottish accent) - this is because she lives in a county on the other side of the river and he refuses to say her real name.

'The Witch' although she's not very good at it

'It'

'Eye of Sauron'... skids go back to Mordor (because they used to bring her here albeit not in person, but in influence)

We call BM Fiona... as in Shrek's Wife. The resemblance is scary. 

Back when SD2 was in our life, DH always referred to her mother as Psycho (full name was PsychobitchfromHell). A bit derivative since she descends from a long line of mental illness, but then DH has a literal bent to his thinking.

I refer to DH's female relatives as The Coven, because they often cook up bad things and conspire or act in concert. I hope this doesn't offend any Wiccans.

A couple other nicknames are Nordstrom (a brittle, often artificial snob overly concerned with appearance) and Meddling or The Meddler. Not very original, but I was aiming for accurate.

BM is Bowling Ball Basement BM (B3BM). Bowling Ball because she is shaped liked a bowling ball, and she retired with no money and moved into SD's basement and will likely be there forever.

We call BM2 Voldemort or Voldie for short... because she's pale, evil and her (real) name should never be spoken!

OSS i called pumpkinhead.  He has zero facial bone structure (like Chef now that he's overweight).  a big pasty white blob like the "no soul" meme with two dots for eyes. 

SD has Chef's hair (curly dark blonde) and face.  I called her dominatrix as she is a bossy, mean girl and animal torturer. 

YSS I used to call Prince Hygiene aka the House Shitter.  He shit all over my house literally out of anger for not getting his way.  Homely child with a big nose and orangey urine colored hair

Girhippo is half Giraffe and half Hippopotomus.

Lol.

These are fun. 

My family used to call OSD “LBR” (for Little Black Raincloud) and “Ughhhhh” (as in...OSD is coming?? Ughhhhh...)