I thought I’d start with a topical word, one whose etymology people often mistake for a compound of the French adjective bon ‘good’ + fire. This is understandable given the spelling, and the number of French loanwords found in English, but the true etymology becomes apparent when we look back to the word’s earliest spellings: bonefire and the Scottish banefire.
The name derives from the practice of burning bones, which was common up to the 18th century. These fires were often associated with religious celebrations, as the following quotation from the 15th century makes clear: ‘In worshyppe of Saynte Johan the people waked at home, & made 3 maner of fyres. One was clene bones and noo woode, and that is called a bone fyre.’ Once this practice had ceased, and the vowel of the first syllable had been shortened in pronunciation, the association with the burning of bones was lost. In his dictionary of 1755, Dr Johnson defined the word as ‘A fire made for some publick cause of triumph or exulation’, claiming that the word’s etymology was from French bon and establishing the spelling bonfire that we still use today.