Welcome back to BRAIN NUTRITIONAL HEALTH! NOTE: Before I begin this article on the history of mustard seed, I decided to write it only because the seed itself has good properties - even medicinal uses, as we will see. However, it tends to be drowned in vinegar these days, and the condiment is mostly made with GMO white vinegar and other ingredients like not-good colorings. I've excluded modern history of mustard seed use for that reason. Please see "Not the Same: GMOs" for more on GMOs in general in the following: (LINK)
Mustard seeds have been found in the ruins of communities from the Stone Age, and there are at least 40 species of the plants. Some of the more-used kinds used for condiments are black mustard, hailing from Asia Minor and the Middle East; brown Indian mustard, a Himalayan plant; and white/yellow mustard, hailing from the Mediterranean basin(1). Some claim that Ancient Egypt was the initial source of mustard(2) - archaeological evidence seems to to indicate it was used to flavor food there and King Tut's tomb definitely had mustard seeds in it. Sumerians of ancient Iraq made a paste of mustard seed and put it in verjus, the very acidic juice of unripe grapes. Farming mustard seeds helped bolster prosperity on the Sumerian urban scene(1).
The Greeks used mustard seeds as a pretty broad-spectrum medicine - for such things as snakebite, hysteria, and the plague. Indeed, in the modern world, we've found that they contain powerful nutrients like anti-inflammatory minerals "manganese, iron, magnesium, and selenium" which may help cut down on symptoms of such conditions as arthritis and asthma. The Vitamin B3 and niacin help lower cholesterol and, among other things, help digestion. Possibly early as the 500s BC, mustard seed was used for scorpion stings by Pythagoras; Hippocrates(1) [of the medical oath] "used mustard in medicines and poultices" in the following century. Plasters of mustard were used, among several uses, for toothaches(1).
The Romans put ground mustard seed into wine and introduced mustard to Spain(1) and the north of France, where monks began cultivating it. Monasteries actually made rather hefty profits from mustard by the 800s. The word "mustard" is actually thought to come from grape must, the unfermented grape juice it was mixed with so commonly(2). An official Vatican position for a mustard maker was made by a mustard-enamored pope(1,2). Explorer Vasco de Gama brought mustard to India(1).

References:
1. Sherman, Carol. "Mustard: history of the yellow seed." Hektoen International: A Journal of Medical Humanities. Hektoen International. 18 Feb. 2020. Web. 1 Sep. 2021. https://hekint.org/2020/02/18/mustard-history-of-the-yellow-seed/#.
2. "Home/About us/." G. S. Dunn Dry Mustard Millers. G. S. Dunn Dry Mustard Millers. Web. 1 Sep. 2021. http://www.gsdunn.com/english/?page_id=2943.

Welcome back to Brain Nutritional Health! While most of the way through the Immune System series we just technically saw the end of, I had the nudge to look up the lymphatic system, of which I more than anything merely knew the name and that it needed stimulation. What I learn beyond the name of something really ends up inspiring much of the articles here and in sister blog Rainbows of Autism. Let's embark on what is really a continuation of the Immune System series!
The lymphatic system truly has a most key role in the immune system and checking inflammation as, beside balancing fluids and carrying "protein molecules, salts, glucose and other substances," it flushes pathogens (invaders) away to be dealt with(1). It is considered part of the circulatory system(1,2) and has its own "veins, arteries and capillaries" much smaller than blood vessels for circulation of lymph fluid(1); capillaries push the fluid into surrounding tissue, where it collects toxic and infectious substances into traps(1,2) in such places as "the throat, groin, armpits, chest and abdomen"(1) - those traps are the lymph nodes, and they have more ingoing than outgoing portals so that lymph fluid stays around inside(1,2) for dealing with of the nasty substances brought in before return to circulation(2). 
There are further elements to the entire lymphatic system besides vessels and nodes. Tonsils execute pre-digestion filtration of bacteria(1). [They aren't so vestigial after all!] Adenoids guard "the entrance to the digestive system and lungs" from a position behind the nose. Spleen and thymus "scan the blood and produce white blood cells"(1).
Temporary elevation of stress from fear, including such kinds as anticipation from riding a roller coaster, causes the immune system to ramp up; escalation of heart rate attends the spleen releasing extra red and white blood cells, the red increasing oxygen levels and the white increasing the power brought to bear on impure substances. Prolonged stress instead checks the power of immune response. Modern life means unprecedented double duty for the immune system as it now faces multiplied exposure to toxic substances(2). This means natural detoxification is part of immune health. Lymph nodes swell with infections. Illness and injuries cause swelling of fluid which causes pain(1). Two minutes spent on a mini trampoline actually stimulates the lymphatic system, flushing it and tripling white blood cells in the body. Spreading out two-minute bouncing sessions works better than one big chunk for the day(2).
Please see nutrients to fuel the immune system in our previous article from two weeks ago, "Immune System Part 3: Immunity Nutrients." 

References:
1. Levy, Jillian. "The Lymphatic System: How to Make It Strong & Effective." Dr. Axe. Dr. Axe. 24 Oct. 2015. Web. 23 Aug. 2021. https://draxe.com/health/lymphatic-system/.
2. "Strengthen The Lymphatic System." Promolife Blogs & Articles. Promolife, Inc. Web. 23 Aug. 2021. https://www.mypromolife.com/blog/2014/12/strengthen-the-lymphatic-system.