Fag
The term fag derives from the word "flag" (as in: "His strength was flagging."). "Flag" appeared in the sixteenth century and was apparently a variant of the Middle English word flacken. Flacken meant "to flutter, and was influenced by the Old French word flaquir. Flaquir meant "to be flaccid." The word "fag" came to mean "thing hanging loosely," and was applied to the remnants of a bolt of cloth, the tail end of an originally long spool of rope, etc., It therefore had the derived meaning of any off-cut or unwanted part of any product, such as wood, cloth or meat, known as a "fag-end." The associations among the various strands of meaning of "fag," such as "to flutter," "to be flaccid," "thing hanging loosely," "the last and worst part of anything" seem to be better connected to the pejorative present-day sense of "faggot" and "fag" than are the dictionary meanings of the word "faggot," which were limited strictly to the sense of "bundle" before the middle of the twentieth century.In British English, the word "fag" was used (as a verb and a noun) to refer to a kind of apprenticeship practiced within public schoolss. Younger boys within the school "fagged" for the older boys by cooking breakfasts, cleaning sports kit or other menial tasks. The term fag in this sense derived from the sense "flagging in energy due to having performed strenuous menial labour," as in "I'm all fagged out." Violence, bullying and sexual abuse were sometimes associated with fagging. As public schools have become more exposed to public scrutiny, fear of litigation has caused the practice of fagging to be banned in most schools.
"Fag" is also used as a colloquialism for a cigarette, as in "I'm gasping for a fag", "Where can I get some fags?", or "Can I bum a fag?" (can I borrow a cigarette?). It was originally a reference to a cigarette-butt or cigar-butt and comes from the expression "fag-end," meaning the leftover or useless part of any thing.
There is another interpretation according to which the word faggot is the full form of the term of abuse for male homosexuals.