Medicine comes from the Latin [ars] medicina, from medicus (physician), from medeor (to heal). The root mad- or med- occurs in several languages: middle Persian madha (medical science, wisdom); Sanscrit medha (intelligence, wisdom); ancient Greek medos (advice), medomai (to think about). Consider also words such as meditate, from the Latin meditari.
I'd venture to say that med- or mad- was a paleo-indoeuropean root related to considering, advising or knowledge. In archaic times, giving advice on how to treat illnesses must have been the prerogative of the learned man, the priest. It turns out, then, that using "medicine man" for "shaman" might have been more appropriate than it seems at first.
Chiffy
"Etymologicon Magnum, or Universal Etymological Dictionary" by Walter Whiter (1800) makes the claim that "chiffy", as used in the term "in a chiffy" derives from the Anglo-Saxon word "Caf".
"A Dictionary of the Anglo-Saxon Language" by Joseph Bosworth (1832)
confirms the meaning of "Caf" as "quick, sharp, nimble, swift".
Jiffin
This is my oldest source yet, this time for "jiffin".
"The Fall of British Tyranny: or American Liberty Triumphant" by John Leacock
This was published in MDCCLXXVI, which by my reckoning is 1776.
Please to walk aft, brother soldiers, that's the fittest berth for you, the Kidnapper's in the state room, he'll hoist his sheet-anchor presently, he'll be up in a jiffin --- as soon as he has made fast his end of his small rope athwart Jenny Bluegarter and Kate Common's stern ports."
Jiff/Jiffy
In 1791, Edward Nairne of Sandwich, Kent published "Poems, Miscellaneous and Humorous, with Explanatory Notes and Observations" in which the following lines appear:
At dinner-time, and bus'ness slack,
I stept to Joe's, and got a snack
A pot of mildchee, and a whiff,
And off again in half a jiff !§
The author's explanatory notes, below, are expansive and delightful:
§ Jiff or jiffy, a jocular expression, and means a short space of
time. Innumerable are the expressions (particularly amongst sailors)
to shew what expedition may be, or is intended to be made, in the
doing of any act ; the progress of these is curious. I perfectly recol-
lect, when a school-boy, an expression of this kind — ' Before you
can say Jack Robinson' — was very common. After the intervention
of various others, that of — ' As soon as you can say peas' — came
into vogue ; but some persons, who were not over precipitate, very
properly qualified it by adding — ' and boil them.' Next, the ele-
gant expression of doing any thing ' In a pig's whisper' came into
fashion! (What particular period of time this contains, I am at a loss
to determine, having never yet had the pleasure of hearing these melodious animals exhibit in this way ! — I have frequently, and with
admiration, observed them make transitions from one note to another,
and which usually has a most charming effect.) — The ingenuity of
modern times has, I believe, brought this business to its ne plus ultra,
its greatest perfection ! and people can now, according to their own
declarations, do things ' In less than no time ' This beats Joshua's
making the sun stand still -, for that only protracted daylight, and
puzzled the clocksmiths ! but this has all the advantages of time,
without the inconvenience of waiting for it.
Best Answer
Yiddish and Middle High German both appeared relatively close together (respectively originating from around the 9th century and 11th century).
During this period the Middle High German word slange (itself originating from Old High German's slango) for serpent or snake evolved to Yiddish's shlang, until eventually it became the Yiddish word schlong we know today.
How did it get it's traction? Because we are a terribly unoriginal group of people, where anything that resembles a man's penis will become a euphemism for it; see: sausage, weiners, one-eyed snake, stick, hose. However, even in slang form I've never encountered "schlonged" before Trump (although you can immediately understand what it means - it's not that creative).
While the word itself isn't too offensive (euphemisms don't tend to be as their original meanings are innocent enough), the intent behind it definitely is in it's blatant sexism. He deliberately uses the word schlonged because we instinctively know what it means while associating it with the schlong Hillary's presumably lacking. Just like when he mentioned she couldn't satisfy her husband, then questioned how could she satisfy a country; this man knows how to use words and phrases that stick in their vulgarity without being particularly vulgar at all.