Delta, the 4th letter of the Greek alphabet, has the shape of a triangle and thus could represent a 3-dimensional pyramid in 2-d profile.
“Polis” referred to a city state in ancient Greece or, more broadly, a state or society especially when characterized by a sense of community
“Deltapolis” is therefore a pyramidal city or city state.
The Greek lettering is a tribute to classical Greek civilisation and its many achievements, and in particular its City States.