Why do some sources prefix "BOFURI" to the English title of "Itai no wa Iya nano de Bōgyoryoku ni Kyokufuri Shitai to Omoimasu"?
"BōFuri"「防振り」 is the official abbreviation of the title in Japanese.

It is taken from the Japanese title 「痛いのは嫌なので防御力に極振りしたいと思います。」, which reads "Itai no wa Iya nano de Bōgyoryoku ni Kyokufuri Shitai to Omoimasu".

Related: Is there a name for the abbreviated (usually three syllable) title?