I Think It Means Kiss My A**
That probably means, "knit to marker."
There's a video game called Mortal Kombat, and that is it's abbreviation. I'm not sure about other possible MDKs.
'k' is the standard SI prefix for kilo, meaning multiply by 10^3, or 1000. This is the same as km, meaning kilometer, as in 1000 meters. Your example is kilo Watt hours, as a measure of power usage.
The letter K had no particular significance; it was chosen merely to have a phonetically different letter from the letters C and D.
millimeters or M M