What is "blachernitissa"

Blachernitissa , also called Theotokos of Blachernae (Θεοτόκος των Βλαχερνών, Θεοτόκος η Βλαχερνίτισσα) or Our Lady of Blachernae (Παναγία η Βλαχερνίτισσα), is a 7th-century encaustic icon representing the Most Holy Theotokos and Ever-Virgin Mary. It is also the name given to the Church built in honour of the Virgin Mary in the Blachernae section of Constantinople. The name Blachernae possibly derived from the name of a Vlach (sometimes written as Blach or Blasi), who came to Constantinople from the lower Danube