Rosi is a diminutive of Rose names, from Latin rosa meaning rose.
Rosi is a diminutive of Rosa, Rosalia, or Rosario, all of which root themselves in the Latin "rosa" — the rose, that oldest symbol of love, beauty, and transience. The rose carried enormous weight in classical antiquity (sacred to Aphrodite and Venus), in Christian iconography (associated with the Virgin Mary and the rosary), and in later literary traditions where it came to stand for perfection shadowed by mortality.
To name a child Rosa was to invoke all of that, and to call her Rosi was to hold it lightly — to keep the meaning but soften it into everyday affection. Rosi has flourished as a familiar form in German, Italian, and Spanish-speaking cultures, where diminutives are used not to diminish but to express closeness. In Austria and southern Germany, Rosi carries a particularly warm, gemütlich quality — the name of a grandmother's kitchen, of Alpine simplicity, of genuine rather than performed charm.
The mid-twentieth century saw it used both as a stand-alone name and as a pet name, and it remains in gentle use today. Its informality is its virtue: Rosi makes no grand claims, offers no hard edges, and arrives with the easy affection of a nickname that became a name.