Complex sentence: The town is sometimes referred to in Welsh as "Tywyn Meirionnydd", with Meirionnydd here probably referring originally to the cantref of that name which lay between the River Mawddach and the River Dovey.
Split into simpler sentences: The town is sometimes referred to in Welsh as "Tywyn Meirionnydd". This probably originally referred to the cantref of Meirionnydd which lay between the River Mawddach and the River Dovey.