c.1440, "rose garden," from L.
rosarium "rose garden," from neut. of
rosarius "of roses," from
rosa "rose" (see
rose). The sense of "series of prayers" is 1547, from M.Fr.
rosaire, a figurative use of the word meaning "rose garden," on the notion of a "garden" of prayers. This embodies the medieval conceit of comparing collections to bouquets (cf.
anthology and M.L.
hortulus animæ, "prayerbook," lit. "little garden of the soul"). Sense transf. 1597 to the strings of beads used as a memory aid in reciting the rosary.