hiirenherne (Finnish) comes from Finnish herne, from Proto-Finnic herneh, 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.
Ancestry of “hiirenherne”, step by step
hiirenherne traces back through two separate lines of ancestry.