the.com/ammonium

means Ammonium is the positively charged ion, NH4+, formed when ammonia gas grabs an extra hydrogen ion — it's the stable, dissolved, 'behaving itself' form of ammonia you find in fertilizers, cleaning products, and your own urine.

from The trail leads back to 'ammonia,' which chemists named after sal ammoniac, a salt historically gathered near the Temple of Jupiter Ammon in ancient Libya — the story goes that camel drivers' urine (and dung) collected near the shrine, decomposing into the pungent salt. Ammonium itself is simply the 19th-century chemical suffix '-ium' bolted onto that older name, marking it as the cation — the ion form — of ammonia, once chemists worked out it behaved like a metal's positive ion in reactions.