Learn English – What does ‘lick’ mean in this sentence

In this case, "sunshine" is a fairly condescending term of reference for the other person. This slang dictionary writes:

form of address for a person, usually female.

As this forum adds, calling someone sunshine is usually part of giving a threat. This is the context in which your examples use it--each man is threatening the other, so they are referring to each other as "sunshine".

It is difficult to find exact origins for many slang terms, but one possibility is that it is simply a term of endearment being applied sarcastically. This appears with other words, such as "princess".

You can use sunshine as a nickname for people in a positive sense, too. It can often mean that a person is always smiling and happy, warm like a ray of sun.

It can also be used fairly sarcastically, to mean someone who isn't warm and happy. For example, if you wake someone up in the morning and they're grumpy, you could say:

Good morning, Sunshine!

You may differ, finally, but my take on that use of 'artisks' by that character in that work is that it's a malapropism springing from 'artists' via the lips of the sage Mrs. Hall. If you read on, I expect you'll find that the artists do indeed come to the inn in the summer, and that Mrs. Hall has a vaguely disapproving yet tolerant attitude toward those same artists.

Of course, it could just be a typo in an ineptly proofed edition.