means A string of beads used in Catholic devotion to count a sequence of prayers, and the cycle of prayers itself.

from From Latin rosarium, meaning "rose garden" or "garland of roses" — the medieval idea being that each prayer offered up was a rose, and the whole devotion a bouquet woven for the Virgin Mary. The word reached English through Old French rosaire. The flower link runs deep: the very word "bead" comes from Old English bede, meaning "prayer," so a string of beads was literally a string of prayers long before it counted anything.