Bombers, at least during the First World War, were troops trained in the use of throwing hand-grenades, which came into general use after the First Battle of Ypres (19 October – 22 November 1914). The term Bomber was officially adopted after controversy over it's previous title, namely that of "Grenadier."
According to Soldier and Sailor Words and Phrases “The Grenadier Guards objected, claiming that they had a prescriptive right exclusively to the name, as having been specially conferred on them after Waterloo to commemorate their part in overthrowing Napoleon's Grenadiers of the Guard. The Guards, says Sir Frederick Ponsonby, in his History of the Grenadiers in the War, were "much perturbed" considering it as "an infringement of their privileges and misleading." The Colonel in command of the First Battalion Grenadier Guards protested to the War Office against the "usurpation." After a protracted controversy a final appeal was made to the King, and in May, 1916, it was officially announced that "at His Majesty's 'expressed wish' the word 'Bomber' should be universally substituted for 'Grenadier.'” 
In more recent times the term bomber has different connotations and is usually associated with terrorism.
References / notes
- Edward Fraser and John Gibbons (1925). Soldier and Sailor Words and Phrases. Routledge, London p.31-32.
Glossary of terms and customs
This page forms part of our glossary of words and phrases of the Armed Forces of the United Kingdom of Great Britain during the Great War, which also includes: technicalities, trench slang, expressions in everyday use, nicknames, sobriquets, the titles and origins of British and Commonwealth Regiments, and warfare in general. Please feel free to help expand and improve this content.
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