The word 同胞 is formed by combining two characters: 同, meaning "same" or "together", and 胞, which originally refers to the "womb" or "placenta". The concept is built entirely on a biological metaphor, literally meaning "from the same womb". This imagery is then extended metaphorically to represent a profound, familial bond between people who share the same ethnicity or nationality, implying they are like siblings born of the same mother.