What is the meaning of [Imitation is the sincerest form of flattery]

This proverbial expression dates from the early 19th century, although versions of it that paraphrased the same thought existed well before then.

The first of these alternate versions is found in a biography of Marcus Aurelius by Jeremy Collier and André Dacier, titled Emperor Marcus Antoninus his conversation with himself, 1708:

You should consider that Imitation is the most acceptable part of Worship, and that the Gods had much rather Mankind should Resemble, than Flatter them.