From SBS 59.
Odacchi! I noticed an amazing thing!!! It is that if you show the Straw Hat Devil Fruit users in numbers, it will be the numbers from 1~10!!
Luffy→Gomu Gomu (5.6.5.6.), Chopper→Hito Hito (1.10.1.10), Robin→Hana Hana (8.7.8.7.), Brook→Yomi Yomi (4.3.4.3.)
(1.3.4.5.6.7.8.10), but there is no (2.9), so is the one who ate the Nikyu Nikyu (2.9.2.9.) no Mi, Bartholomew Kuma, gonna be a Straw Hat next? Please tell me!!! P.N. SHANKUS.LOVE
O: WHAAAAAT?! (shock) Gosh that surprised me! Why was I surprised?! NO COMMENTTTTTTT!!!!!!!! NEXT!!
Because of how japanese characters work, there's a handful of ways 2 and 9 can be represented, though Kuma has already taken one of them.
Ni Kyu (Kuma's) or Fu Ku (potentially Kinemon's) could work, or some variation thereof.
Fuku could be
clothing (like Kinemons)
luck, fortune
blow/to play the flute
to wipe
Wiping fruit sounds like a weird villain ability, and I think Brook has already got a lock on music and nami on wind stuff. (And a supernova took the bodily instrument thing already) Strawhats are already lucky so that's a rough one. Bad luck maybe?
I don't know how the language well enough to really break it down, so I'm not sure if they can be mixed and match, Ni Ku and Fu Kyu, or done backwards, Kyu Ni and Kufu, and those would open up more options, but thats a translation and pun beyond my paygrade.
If the mix and match of Niku is an option, that would be MEAT, and we know Luffy is all in on that, but after Big Mom's kingdom, well…. also food is Sanji's thing.
Fukyuu would be deterioration/rot, or "in no hurry". It would also be really unfortunate name in English.