Eustace
Eustace is the rendition in English of two phonetically similar Greek given names:
Equivalents in other languages include Ostap (Ukrainian) Eustachy (Polish, Russian), Yevstaphiy (Russian), Eustachio (Italian), Eustache or Eustathe (French), Ustes (Guyanese) and Eustice (English).
The Greek Eústachys is no longer used; Eustáthios (usually transliterated Efstáthios) on the other hand is still popular and often used in the informal or diminutive Στάθης (Státhis).