halm (Middle High German) comes from Old High German halm, from Proto-West Germanic *halm, from Proto-Germanic halmaz, from Proto-Indo-European ḱolh₂mos, from Proto-Indo-European ḱelh₂- — to pierce, strike; to stick; prick; stab.
Ancestry of “halm”, step by step
halm traces back through two separate lines of ancestry.