Naturally, the word "flu" struck terror in the minds of generations to follow, and the smelly cure-all medicine bags appear repeatedly throughout history whenever an outbreak of potential epidemic illness or disease occurs. Babies and school-aged children were forced to wear acifidity bags during outbreaks of polio, measles, and during the winter to stave off influenza.
What is Asafoetida?
Asafoetida is a resin derived from the four-year-old roots of the Ferula asafoetida plant, a member of the fennel species. The plant is cut back at the ground to make a slit in the top of the root for the resin to ooze out, then covered to protect from the elements. This action is repeated until enough of the hardened resin forms a walnut-shaped brown ball for harvest. The brown clump is ground into a powder and mixed with flour and other ingredients for market.
Asafoetida is native to the higher altitudes of the Mediterranean, Middle East, and Central China, Iran, and Afghanistan, and is a primary imported spice to India, an essential ingredient in curries and used as a medicine for centuries (noted in ancient reference dating 400 BC). Use of plant's resinous root juice has appeared in writings of Alexander the Great, medical practitioners in the first century, noted in the histories of ancient Rome, and used as a medicine into the Middle Ages. 
The strong sulfurous odor of asafoetida mellows in cooking, yielding a strong sweet onion-garlic flavor to dishes. Very little of the spice is necessary so a small container lasts a long time. The potent powder is best fried in butter (ghee) to dissipate the smell before adding the remaining ingredients to the pot. The storage of asafoetida requires an airtight container enclosed in a sealable bag (or two) to prevent the smell from contaminating other pantry items.
The powdered resin has a very long list of uses, here are just a few:
During the swine flu pandemic (a similar deadly strain of the Spanish flu virus) in 2009, antiviral drugs were in short supply, vaccines took months to develop, and were expensive ($100 per shot). Scientists in labs worldwide were testing natural home remedies as alternatives for potential unprotected populations. Lab reports proved that asafoetida resin lived up to its historical hype as a cure. The test results found multiple strong antiviral constituents and additional properties much more potent than the costly manufactured treatments. 
With further testing of asafoetida's, researchers also discovered the powerful antioxidant polyphenols were very successful in fighting many forms of cancer and irritable bowel syndrome (IBS). 
It's in the Bag!
I am incorporating asafoetida powder to my pantry of culinary and medicinal herbs and spices! Today's intellectual society may laugh or frown on the malodorous amulets of the past, but history has shown that some home remedies actually have merit! So what will be in your acidity bag if you ever need one?
 Bharat Aggarwal, PhD & Deborah Yost. Healing Spices. Sterling Publishing, NY. 2011
 Botanical.com. A Modern Herbal. Mrs. M. Greive. Pine, White. www.botanical.com/.
 My Indian Food. Asafetida. www.my-indian-food.com/Asafetida.html
"asa" is Persian for gum.
Acifidity bags have as many varied spellings as the asafoetida plant:
Asafoetida was not the only smelly remedy used in an acifidity bag: