Here, fast doesn't mean "(capable of) moving quickly". Much rather, it is being used in the sense "firmly fixed" (see fasten your seatbelts or fast friends). The Phrase Finder says that "This is a nautical term. A ship that was hard and fast was simply one that was firmly beached on land." It adds that the term was used in figurative sense by the early 19th century.
Personally, I don't think it's being used more commonly in the negative. Indeed, a quick COCA search returns 40 occurences of "hard and fast rule" or "hard-and-fast rule", but only 22 of them are using it in a negative context — and I am being as generous as possible there, counting not only "no hard and fast rule" and "not a hard-and-fast rule", but also "don't have any hard and fast rule", "rather than any hard and fast rule", "was never a hard-and-fast rule" and the like.
One thing stands out to me, though: out of 16 occurrences of "hard-and-fast rule", with hyphens, 12 appear in a negative context, or 75%. For the non-hyphenated version, it's almost the other way round: 60% positive, 40% negative. (Again, counting "negative" very generously.)
The figures from the BNC are too small to be statistically meaningful. But anyway, here's an overview:
COCA BNC
total negative total negative
hard and fast rule 24 10 8 7
hard-and-fast rule 16 12 1 1
an early occurrence is from Olympic Games by Isaac Cruikshank:
- In settle (someone’s) hash, to subdue, silence, defeat; kill: s. >,
in C.20, coll. An early occurrence is
in Isaac Cruikshank, Olympic Games, 16
June 1803 (thanks to Mrs M.D.George).
it's also in Americanisms: The English of the New World (1872) by M. (Maximilian) Schele de Vere - here's an image:
![settle one's hash in Americanisms](https://i.stack.imgur.com/52lA4.png)
from hash:
1657, "to hack, chop," from Fr.
hacher, from O.Fr. hache "axe." The
noun "stew" is first recorded 1662,
from the verb.
My educated guess is that it's related to the the origins of the phrase "bury the hatchet", relevant quotes being:
"Bury the hatchet" is an Indianism (a
phrase borrowed from Native American
speech). The term comes from an
Iroquois ceremony in which war axes or
other weapons were literally buried in
the ground as a symbol of newly made
peace. The other two languages spoken
by Europeans in close contact with the
Iroquois in and around what is now New
York state also use the phrase:
enterrer la hache de guerre and de
strijdbijl begraven. (I leave it as an
exercise for the reader to determine
which is French and which is Dutch.)
and
The first mention of the practice in
English is to an actual
hatchet-burying ceremony. Years before
he gained notoriety for presiding over
the Salem witch trials, Samuel Sewall
wrote in 1680, "I writt to you in one
[letter] of the Mischief the Mohawks
did; which occasioned Major Pynchon's
goeing to Albany, where meeting with
the Sachem the[y] came to an agreemt
and buried two Axes in the Ground; one
for English another for themselves;
which ceremony to them is more
significant & binding than all
Articles of Peace[,] the hatchet being
a principal weapon with them."
So between MikeVaughan's answer that it's related to the French word for "axe" & the practice of "burying the hatchets", I'm inferring that "settle someone's hash" came from these ideas.
Best Answer
Similar to the idiom getting your panties in a bunch, I will hazard a guess that jimmies is a complementary masculine phrase. Jimmies may have originally referred to the male member (or accompanying anatomy). At least one instance occurs in the December 2003 issue of Men's Health.
In the article, "in their grip" refers to wearing a condom.
As for rustle, this definition seems likely:
This is just one example of getting your X in a Y or getting your (noun) (verbed) (e.g. getting your titties in a twist, getting your biscuits flipped, and so on). The gist of these expressions is that one is annoyed, angered, or upset. The severity or crudeness of the language may describe the intensity of emotion felt by the "rustled".
Jimmies works as a malleable, polysemic construction. Since it can mean nearly anything, the phrase can be employed in multiple situations, increasing its popularity.