Yes, milady comes from "my lady". Milady (from my lady) is an English term of address to a noble woman. It is the female form of milord.

Understanding the Context

And here's some background on milord: In the nineteenth century, milord (also milor) (pronounced "mee-lor") was well-known as a word which continental Europeans (especially French) whose jobs often brought them into contact with travellers (innkeepers, guides ... Lady Macbeth wants to substitute her milk (which would nourish a kid) for gall, which today would mean boldness and impertinence, but also refers to bile (Merriam-Webster). So here, too, the milk is too kind, too nourishing, and so it must be switched for something more murderous so that she can physically and mentally go through with murder. In case you don't know, in British English, the little red-with-black-spots insect is not called a "ladybug", as in North America, but a "ladybird".

Key Insights

This seems rather a poor act of classification,... The plural possessive is "ladies'." "Lady" is singular, so if you were referring solely to one woman's shoes, it would be "the lady's shoes." As for your second question, I'm assuming you're referring to a group of women in your salutation of them, so it would be "Good morning, ladies." And as you're addressing them directly, the comma preceding "ladies" is necessary. single word requests - Is there an opposite gender for "lady ... I tried searching Google Ngram Viewer for "Look lady" and "Listen lady", both capitalized so as to occur at the start of a sentence, with the hope that these ngrams would reflect the usage of "lady" in a derogatory/dismissive sense. It seems to have come into usage around 1950, and really took off in the late 1990s.

Final Thoughts