"Scholarly purists prefer the laconic Latin title Petrarch himself gave it:
Rerum vulgarium fragmenta. The adjective vulgaris is a lexical description, referring to the fact that the poems are in Tuscan rather than Latin, so the title translates roughly as ‘Fragments of Things in the Vernacular’. The more obvious meaning, ‘Fragments of Everyday Things’, is also present, and perhaps ironic – to be disappointed in love is indeed a common experience, though when viewed through the distorting lens of 14th-century poetry it becomes something complicated and metaphysical. After Petrarch’s death in 1374 the collection acquired more aptly Italian titles.
Rime sparse (‘Scattered Rhymes’) is taken from the opening lines of its first poem: ‘Voi ch’ascoltate in rime sparse il suono/di quei sospiri ond’io nudriva ’l core’ (‘You who hear in scattered rhymes the sound of those sighs I fed my heart with’). The most popular title is even simpler:
Il Canzoniere (‘The Songbook’), which seems to express a sense of the work’s definitiveness as a collection of lyric poetry."
Charles Nicholl LRB