The idiom "栩栩如生" is formed by combining the reduplicated term "栩栩", meaning vivid or lively, with the phrase "如生", meaning "as if alive". The character "栩" originally refers to an oak tree but is used metaphorically here for vitality, while "如" means "like" and "生" means "life" or "alive". This structure yields a compound describing something so realistic it appears lifelike.