+ Finnish and the dialects.
Not all of the names I've listed here are equally popular. Some are probably half-forgotten and some are only used in certain regions.
Ämmä has gained a pejorative meaning in many places;
muori is known especially as the wife/partner of Santa, but perhaps also used by some as 'grandmother'.
Mummu, mummi and
mummo have spread across Finland.
Mumma, momma, isu are markedly Southern Ostrobothnian.
Fammu and
tummu are used in Western coast. Similarly,
tuhva, tuffa are known in Satakunta (South West) - these are loans from Swedish
storfar, sturmur and
farmor.
Paappa, paapa are Southern Ostrobothnia names.
Pappa, ukki, vaari are used everywhere in Finland AFAIK. (Note that I've lived all my life in West Finland, so I don't know for sure what names are used in East or North.)
Kotus (which is the source I've used for this) also says that
akka could've meant 'grandmother' at some point. In spoken language, it's usually pejorative word for '(old) woman' but I wouldn't be surprised if it had meant 'grandmother', since we have
ukko for 'grandfather'. Also, North Sami
áhkku is quite close to
akka; even if the words weren't related, I could imagine people living in the same area where
áhkku is/was used would call their grandmothers
akka. (But that's just speculation!)
I haven't heard anyone using the words with
vanha- or
suur- prefixes, but my family has a system where grandparents are called
mumma and
paapa, and great-grandparents are
vanhamumma and
vanhapaapa.
bedstemor, bedstefar / (father's side): farmor, farfar / (mother's side): mormor, morfar
Großmutter, Großvater / (diminutives): Oma, Opa
grootmoeder, grootvader / oma, opa
grandmother, grandfather
diminutives: grandma, grandpa / gramma, grampa / granny, gramps / (southern S): mamaw, papaw [ˈmæmɔ/ˈmæmɑ], [ˈpæpɔ/ˈpæpɑ]
amma, afi
bestemor, bestefar
(father's side) farmor, farfar / (mother's side) mormor, morfar
babička, děda / (diminutive) dědeček / (dialect) stařenka, staříček
бабушка, дед (diminutive дедушка)
abuela, abuelo / (diminutives) abuelita, abuelito / (Argentina) nona, nono / (diminutive for either gender) abue
grand-mère, grand-père (diminutives) mamie, papy/papi / mémé, pépé / mémère, pépère
vanaema, vanaisa / vanamemm, vanataat / emm, ätt
isoäiti, isoisä / (mother's side): äidinäiti, äidinisä / (father's side): isänäiti, isänisä
[dialects] GRANDMOTHER: ämmä, ämmi, ämmö, muori, mamma, nanna (nenna), mummu, mummo, mumma, momma, mummi, fammu (vammu), famu (faamu), vammu, tummu, muffa, murfaari
[map], isoäiti (iss-äiti, isooäitee, isuäitee, isu), isomamma, isomuori, suuräiti, suurämmä, suurmummo, vanhaäiti
[map]GRANDFATHER: ukko (ukkovaari; father's side: ukkoisä, kotiukko; mother's side: kirkkoukko, kyläukko), ukki (ukkivaari), äijä (äijäfaari), äiji, äijö, vaari, pappa, paappa (paapa), taata, tuffa (tuhva), tuora, tuhari, vaija, fasfaari, förfaari, faffa, fafa, fappu, faateri
[map], isoisä, isopappa, isotaata, isovaari, suurisä (suuri, suusa, suusi), suurpappa, suurtaata (suta, suuti, suutu, suutti), suurtaatto, suurukko (surkko, surkka, suurkko), vanhaisä
[map] ämmä, äijä
(father's side): пöч, ыджыд ай / (mother's side): ыджыд мам, ыджыд бать
vanājemā, vanāizā / vanāǟma, vanātǭți / (father's side) izājemā, izāizā
babo, didi
кова, коча
(father's side): баба, атя / (mother's side): щава, щятя
(father's side) маласо баба, покштя / (mother's side): васоло баба, васоло покштя
ákku, äijih
āка, āйй
áhkko, áddjá
áhkku, áddjá
áhkka, áddjá
aahka, aajja / (father's side) aehtjaahka, aehtjaajja / (mother's side) tjidtjaahka, tjidtjaajja
áhkká, ájjá
песянай, песятай
baboi, dedoi / bab, ded
ämme, äije / ämmä, äďďä / baabuška, ďeeduška / baba, ďeda
vanaimä, vanaesä / memm, tätä / äidi, teeda
дәү әни, дәү әти / colloquial: әби, бабай
энекэ (эбэкэ, эвэ), амака
(father's side) pog, yawg / (mother's side) niamtais, yawmtxiv
(father's side) puj, yawm / (mother's side) namtais, yawm
dux, ong
(father's side) bà nội, ông nội [nội: 內] / (mother's side) bà ngoại, ông ngoại [ngoại: 外] / (grandparents in general): ông bà
kupunawahine, kupunakāne / kuku wahine, kuku kāne / (diminutive for either gender) tūtū