Close.
Actually, “gopher” in Hebrew is separate from “kopher”. It is derived from an unused root word, probably meaning to house in: a kind of tree or wood (as used for building: apparently the cypress. (Ref: Strongs)
You nailed the kopher. Betumin, along with the henna plant for dyeing. (Ref: Strongs)
The KJV translators didn’t need to translate the OT Hebrew because it was the Hebrews themselves (the Masoretes) that added a full system of vowels between 600-950AD, allowing it to be printed five centuries later. (Ref: Unger’s pg 883).
Another example of God keeping His promise to preserve His Word. (Ps 12:6-7)
Is blueletterbible’s (through Gesenius’s lexicon) explanation plausible?
GFR (or GPR) = cypress (Gk. kuparissos)?
(Latin cupressus)?
Now in Latin, C was often interchangeable with G (say Gaius and Caius).