ziarenko (Polish) comes from Polish ziarno, from Proto-Slavic zьrno, from Proto-Balto-Slavic *źírˀnan, from Proto-Indo-European ǵr̥h₂nóm, from Proto-Indo-European ǵr̥h₂nós, from Proto-Indo-European ǵerh₂- — to grow old, to mature.