"Dog" meaning in old English language [closed]

I read these sentences in "The life of Samuel Johnson":

JOHNSON: You HAVE Lord Kames. Keep him; ha, ha, ha! We don't envy you him. Do you ever see Dr. Robertson?
BOSWELL: Yes, Sir.
JOHNSON: Does the dog talk of me?
BOSWELL: Indeed, Sir, he does, and loves you.

Does "dog" in this context mean the person Dr. Robertson, or is there an archaic meaning to imply best friend?

Solution 1:

From The Life of Samuel Johnson, LL. D. by James Boswell we learn the depths of Dr Johnson's contempt of Dr. Robertson:

It is to be regretted that Mr. Boswell should have persisted in repeating these assertions.Dr, Johnson, on every occasion, seems to have expressed a great contempt for Dr. Robertson's works - very unjustly indeed; but however Mr. Boswell might lament Johnson's prejudice, he was in fact not justified in thus repeatedly misstating the fact. [text goes on to cite 2 more examples where Boswell further suppresses and misrepresents Johnson's opinions of Dr. Robertson]

With this contempt in mind, the sense of: OED

a term of reproach or abuse: a worthless or contemptible person; a wretch, a cur.

seems to set the stage for supporting a contemptible person.

And early use cited:

c1330 Richard Coer de Lyon in Englische Studien (1885) Drisses now ȝour mangunel..& scheteþ to hem wiþ alblast, Þe teyled doggen to agast.

Dog has many senses and some date to ~1200 A.D. Ugly ladies and rotten gentlemen have senses of "dog" and "sup, dog?" is modern and benign. But here (your question) the snarky, negative connotation cited is, IMHO, in use.