The earliest use of Italian in a written document can be traced back to a trial held between March 960 and October 963. Judge Arechisi had to sort out a dispute between a land owner, Rodelgrimo of Aquino, and the abbot of the monastry of Montecassino, Don Aligerno.

If the abbot could prove that the monastry had cultivated some lands owned by Rodelgrimo for more than thirty years, the Judge would apply the right of usu capione and transfer ownership of the lands to the monks.

Among the witnesses called to testify were Teodomondo, deacon and monk, Mari, cleric and monk, and Gariberto, cleric and notary. Since the sworn testimony had to be notarized in a language understood by all the interested parties, the witnesses couldn't use Latin, a language by then used only by the higher classes.

This is the formula agreed upon, and pronunced holding Rodelgrimo's papers (first the original version, then modern Italian, then English):

Sao ko kelle terre
So che quelle terre
I know that those lands

per kelle fini
per quei confini
whose boundaries

que ki kontene
che qui sono contenuti
are here described

trenta anni le possette
per trenta anni le possedette
were held for thirty years

parte sancti Benedicti.
la parte di San Benedetto.
by the side of Saint Benedict.

It goes to show that since the very beginning Italian was a language admirably suited for squabbling.