The most I've been able to find out about Fijian cultivars (although some info may have changed over the years) is that they have several different cultivars that they name as a description of each plant's specific appearance. And secondly they name the part of the plant used.
Waka:Lateral Roots,
Lewena:The Underground Stump,
Kasa:The 1st few nodes or internodes of the stem.
Cultivar names include:
-Vula kasa leka (vula='white', kasa='internode', leka='short')
-Loa kasa balavu (loa='black', kasa='internode', balavu='long')
-Loa kasa leka
-Dokbana vula
-Qila leka
-Qila balavu
-Matakaro leka
-Matakaro balavu
-Damu
-Qila bulavu
-Honolulu
Commercially,
loa kasa leka and
loa kasa baluva were the main exports.
Although I've personally never seen any website sell Fijian kava by it's actual cultivar name. I only people sell it as fiji waka or lewena. I've also never seen the 'kasa' grind for sale. The lateral roots have the most kavalactones and I think they also always have more dhm/dhk...so even if the chemotype has a good amount of Kavain there will still be a good balance of heavier lactones in there. 'Lewena' root stump grind is lighter and more kavain-centric.
I looked up the word 'tuki' too and came up with the word 'hammer'. so that fits with kavadudes description 'to pound'.
I agree it probably describes what it does to you or how it was prepared.
I still haven't found a list of Fijian chemotypes though

Also, it seems as though different vendors have different fiji wakas. Some seem to be more kavainy and some seem to be less. But they all seem to be fairly balanced and don't fall completely on one side of the spectrum or the other.
And regarding Wakacon as a vendor. I've never had 'em. But I'm guessing it's legit because I see it's from Salt Lake City, which happens to have a fairly big Tongan/Samoan community.