In the U.S. military, fragging refers to the act of attacking a
superior officer with a fragmentation grenade. The term originated in
the Vietnam War and was most commonly used to mean assassination of an
unpopular officer of one's own fighting unit, often by means of a
fragmentation grenade, hence the term. Although the term is derived
from the grenade, the act was more commonly committed with firearms
during combat in Vietnam

A hand grenade was often used because it would not leave any
fingerprints, and because a ballistics test could not be performed (as
it could to match a bullet with a firearm). The grenade would often be
thrown into the officer's tent while he slept.

In WW 1.An unpopular sergeant was killed when one of his men came up
behind him and dropped an unpinned hand grenade down his trousers.
Thus the term : hot pants.

Sometimes the intended victim would be 'warned' by first having a
smoke grenade thrown into his tent. If he persisted in antagonizing
his men, this would be followed by a stun grenade, and finally by a
fragmentation grenade.

A fragging victim could also be killed by intentional "friendly fire"
during combat. In this case, the death would be blamed on the enemy,
and, because of the dead man's unpopularity, the perpetrator could
assume that no one would contradict the story

After the My Lai Massacre, when interviewed by investigators, soldiers
serving under Lieutenant William L. Calley Jr. disliked him so much
that they considered fragging him. They should have and it's not to
late.

Fragging most often involved the murder of a commanding officer (C.O.)
or a senior noncommissioned officer[citation needed] perceived as
unpopular, harsh, inept, or overzealous. Many soldiers were not overly
keen to go into harm's way, and preferred leaders with a similar sense
of self-preservation. If a C.O. was incompetent, fragging the officer
was considered a means to the end of self preservation for the men
serving under him. Fragging might also occur if a commander freely
took on dangerous or suicidal missions, especially if he was deemed to
be seeking glory for himself.

The very idea of fragging served to warn junior officers to avoid the
ire of their enlisted men through recklessness, cowardice, or lack of
leadership. Junior officers in turn could arrange the murder of senior
officers when finding them incompetent or wasting their men's lives
needlessly. Underground GI newspapers sometimes listed bounties
offered by units for the fragging of unpopular commanding officers.
[citation needed.

Throughout the course of the Vietnam War, fragging was reportedly
common. There are documented cases of at least 230 American officers
killed by their own troops, and as many as 1,400 other officers'
deaths could not be explained.Incidents of fragging have been recorded
as far back as the 18th century Battle of Blenheim.

Ref. Hedges, Chris (2003). What Every Person Should Know About War.
Free Press. ISBN 0-7432-5512-7.

Remember From Here To Eternity:
Private Robert E. Lee "Prew" Prewitt (Montgomery Clift) is a loner who
lives by his own code of ethics and communicates better with his bugle
than he does with words. Prew's best friend is wisecracking Maggio
(Frank Sinatra, in an Oscar-winning performance that revived his
FLAGGING career), who has been targeted for persecution by sadistic
stockade sergeant Fatso Judson (Ernest Borgnine).