Short answers, pulled from the story.
The Sanskrit root dhru means to hold or maintain, defining dharanis as mnemonic devices within Buddhist tradition. Early communities used these chants to ground and remember teachings that were not yet written down.
By the second century BCE, dharanis became acknowledged as essential tools for retaining doctrine. It was only during a third council in Kashmir that scholars put teachings into writing for those who lacked the power of memory.
The earliest extant example dates from around 650 to 670 AD found in Xi'an during the Tang dynasty. This fragment called Great Spell of Unsullied Pure Light used woodblocks for mass production.
Eugène Burnouf was among the first scholars to recognize their widespread importance within Buddhist texts. Moriz Winternitz later agreed they constituted a large part of Mahayana Buddhism while serving as protective spells.
Paritta texts serve as protective charms within Theravada communities across Southeast Asia. Lay devotees traditionally invite monks into homes for rites against evil spirits and calamities.