late 14c., bonfir, banefire, “a fire in which bones are burned;” see bone (n.) + fire (n.). The original specific sense became obsolete and was forgotten by 18c. The general sense of “large open-air fire from any material for public amusement or celebration” is by mid-16c. and that of “large fire for any purpose” from 17c.
also from late 14c.
For anyone wondering
https://www.etymonline.com/word/bonfire#etymonline_v_15587
late 14c., bonfir, banefire, “a fire in which bones are burned;” see bone (n.) + fire (n.). The original specific sense became obsolete and was forgotten by 18c. The general sense of “large open-air fire from any material for public amusement or celebration” is by mid-16c. and that of “large fire for any purpose” from 17c. also from late 14c.