How can two seemingly unrelated species that live in isolation from each other evolve into identical forms?

"Cabbage" is also a part of common names for several unrelated species.

Deflection eye-spots are found in a wide variety of quite unrelated species.

Names using such widespread words as "warbler" for multiple groups of unrelated species were let stand.

But they knew right away that this one was different, because it involved dozens of unrelated species and had no obvious cause.

The term samphire is used for several unrelated species of coastal plant.

On the other hand, many other, unrelated species also have common names ending with cod.

The common name umbrella plant can refer to several unrelated species:

The common name "sage" is also used for a number of related and unrelated species.

Later, it was raised to genus level, and several unrelated species were included.