"Mardyn" is a unique spelling of the name "Marden". The pronunciation of the name is /ˈmɑːrdən/ according to the IPA phonetic transcription. The first syllable sounds like "mar" and the second syllable sounds like "den". The "y" in the spelling of "Mardyn" is an alteration of the standard "e" in "Marden". Although the spelling may be unconventional, the pronunciation remains the same. It's important to note that names can be spelled in different ways, but the pronunciation often stays consistent.
There doesn't appear to be a commonly known etymology for the word Mardyn. It could be a proper name in a specific context or a fabricated word without a specific origin or meaning. Without further information or context, it is difficult to determine the etymology or the intended meaning of Mardyn.