Iseut/Isolde etymology: Celtic?

From: Joao S. Lopes
Message: 68348
Date: 2012-01-04

Is there a secure etymology for Iseut/Iseult, Isolde from Tristan & Isolde? Esyllt could derive from ON i:shilDr, but we could relate this name to Latin or Breton origin?

JS Lopes