The Vietnamese word "ngũ huynh" (or "ngũ huynh đệ") is a somewhat old-fashioned term that refers to your modest elder brother or elder siblings in general. It conveys a sense of respect and acknowledgment of their experience and status in the family hierarchy.
"Ngũ huynh" is a respectful way to refer to your elder siblings, reflecting the cultural importance of family hierarchy and respect in Vietnamese society.