Complex sentence: Any similarity to the name "Milesians" as applied to the ancient Greeks of Miletus is coincidental and should not be confused with the neolithic seafaring Galicians who introduced the celtic language.
Split into simpler sentences: Any similarity to the term "Milesians" as applied to the ancient Greeks of Miletus is coincidental. Nor is the term to be applied to the neolithic seafaring Galicians who introduced the celtic language.