The origin of the conventional May devotion is still relatively unknown. It is certain that this form of Marian devotion began in Italy. There, in May 1784, at the church of Camillians in Ferrara for the first time May devotions were held publicly throughout the entire month. Until then it seems that May devotions were more likely a private exercise of piety, even when also partly in a public framework. Around 1739, for instance, witnesses speak of a particular form of Marian devotion in May in Grezzano near Verona. In 1747 the Archbishop of Genoa recommended the May devotion as a devotion for the home. In Rome by 1813, May devotions were held in as many as twenty churches.
From Italy, May devotions soon spread to France. One of the most prominent promoters was Rev. Pierre Doré (1733-1816) from Longwy in Lothringen. Doré learned of this form of devotion in Italy. May devotions spread in connection with the strong restoration movement after the revolution. They were understood as “the ecclesial contrast to the frivolous spring celebrations of the revolutionaries.†Indeed, from 1830 on, May devotions were celebrated everywhere. …
In Belgium the May devotions -– at least as a private devotion –- were also known since already in 1803 and in 1819 corresponding devotional books were published. … Also in Luxembourg sometime around 1840 May devotions were known. In Luxembourg May received an additional imprint through the annual Mary octave in honor of Mary as “Consolation of the Afflicted. In Switzerland in 1808, this devotion was celebrated for the first time in the College at Brigg (Sitten) … and also publicly since 1849 at the Monastery in Einsiedeln. In the Canton of Glarus the Monastery Näfels was the transmitting center of the May devotion from 1852 on. Around 1860, the Sunday “May sermons†became customary and soon became a specific characteristic of this Mary month.