Short answers, pulled from the story.
Filippo Buonaccorsi, also known as Callimachus, was an Italian humanist, writer, and diplomat born in San Gimignano on the 2nd of May 1437. He is significant for his diplomatic career in Poland, his Latin biographies of Polish historical figures, and for being credited with the first Western use of the word "Balkan" in a letter written in 1490.
Buonaccorsi fled Rome in 1468 after being implicated in a supposed assassination attempt on Pope Paul II. He was a member of the Rome Academy of Julius Pomponius Laetus at the time, and the conspiracy charges made remaining in Rome too dangerous.
Buonaccorsi served as tutor to the sons of King Casimir IV Jagiellon and rose through Polish court ranks, becoming royal secretary in 1474, ambassador to Constantinople in 1476, and the king's representative in Venice in 1486. His influence peaked when one of his former pupils became John I of Poland.
Buonaccorsi first used the word "Balkan" in a letter written in 1490 to Pope Innocent VIII, signing it as Buonaccorsi Callimaco. The letter referred to the Bulgarian mountain range, and scholars credit this as the first Western use of the term.
Buonaccorsi is best remembered for his biographies of Bishop Zbigniew Oleśnicki, Bishop Gregory of Sanok, and King Władysław III of Poland. He wrote in Latin under the name Callimachus and also composed Latin poetry.
Buonaccorsi's tomb is located in Kraków's Basilica of the Holy Trinity. It was created by Veit Stoss, a prominent sculptor of late medieval central Europe.