Complex sentence: Medford was settled in 1630 as part of Charlestown, when Thomas Dudley referred to it as "Mistick" (a name which persisted for many decades), which his party renamed "Meadford".
Split into simpler sentences: Medford was settled in 1630 as part of Charlestown. The area was originally called "Mistick" by Thomas Dudley (a name which persisted for many decades) until party renamed the area "Meadford".