Smyrna, Strong’s G4667 is a noun meaning “myrrh”.
Frankincense and myrrh are both resins — dried tree sap — that come from trees of the genus Boswellia (frankincense) and Commiphora (myrhh), which are common to Somalia.
~ HowStuffWorks. (n.d.). “What are frankincense and myrrh?”
The actual word “myrrh” comes from the Aramaic “murr” for “bitter” (Wikipedia, “Myrrh”; cf Ru 1:20). Indeed, Jesus’ message to the Church in Smyrna was short but obviously intended to encourage, as He acknowledges their “tribulation”, “poverty” and how they “suffer”.
Part of that encouragement is reminding them that He died and was raised again, then telling them to be “faithful unto death”. Myrrh was often used in embalming. It was one of the gifts the “wise men” gave Jesus, signifying His death, and we see in the Bible it was one of the spices purchased after Jesus’ death.
Myrrh is known as an antiseptic as well. Both frankincense and myrrh have been used medicinally for a digestive aid in China.
Interesting that we can find healing even after death through Jesus no matter how bitter our circumstances, and that was part of His message to Smyrna.