June 5th was the day St. Boniface was martyed.

"England is supposed to have been the first place where his martyrdom was celebrated
on a fixed day. Other countries followed. On 11 June, 1874, Pope Pius IX extended
the celebration to the entire world. Brewers, tailors, and file-cutters have chosen 
St. Boniface as their patron, also various cities in Germany. The writings of St. Boniface
which have been preserved are: "Collection of Letters"; "Poems and Riddles"; "Poenitentiale";
"Compendium of the Latin Language"; "Compendium of Latin Prosody"; "Sermons" (doubtful)." 
 
FRANCIS MERSHMAN 
Transcribed by Michael C. Tinkler
 
The Catholic Encyclopedia, Volume II
Copyright © 1907 by Robert Appleton Company
Online Edition Copyright © 1999 by Kevin Knight
Imprimatur. +John M. Farley, Archbishop of New York