Bugger or "buggar" is a slang word. In the United Kingdom, the term is a general-purpose expletive, used to imply dissatisfaction, or to refer to someone or something whose behaviour is in some way displeasing or perhaps surprising. In the US, particularly in the Midwest and South, it is a slang but not offensive noun meaning "small critter."
The term is used in the vernacular British English, Australian English, New Zealand English, South African English, Indian English, Pakistani English, Caribbean English, Malaysian English and in Sri Lankan English.
It is derived from Anglo-Norman bougre, which has also given the term buggery.
Bugger—also bowgard, bouguer (ancient French – bougre): from Latin – Bulgarus, a name given to a sect of heretics who were thought to have come from Bulgaria in the 11th century, afterwards to other "heretics" to whom abominable practices were imputed in an abusively disparaging manner.
The term is thought to have started around the early 13th century, after Pope Innocent III and the northern French kingdom went on the Albigensian crusade in southern France, which led to the slaughter of about 20,000 men, women and children, Cathar and Catholic alike and brought the region firmly under the control of the King of France. The brutal crusade was directed not only against heretical Christians, but also against the nobility of Toulouse and vassals of the Crown of Aragon. The populace of Provence and Northern Italy sympathized with the victims of the crusade because of their moral purity. It was then that the Catholic clergy launched a vilifying campaign against them, associating them with unorthodox sexual practices and sodomy.