Rontu

Finnish

Possibly from a vernacular form of Russian Роман (Roman) or of Russian Геронтий (Gerontij).^[1]

Rontu

Inflection of Rontu (Kotus type 1*J/valo, nt-nn gradation)
nominative		Rontu	Ronnut
genitive		Ronnun	Rontujen
partitive		Rontua	Rontuja
illative		Rontuun	Rontuihin
		singular	plural
nominative		Rontu	Ronnut
accusative	nom.	Rontu	Ronnut
accusative	gen.	Ronnun	Ronnut
genitive		Ronnun	Rontujen
partitive		Rontua	Rontuja
inessive		Ronnussa	Ronnuissa
elative		Ronnusta	Ronnuista
illative		Rontuun	Rontuihin
adessive		Ronnulla	Ronnuilla
ablative		Ronnulta	Ronnuilta
allative		Ronnulle	Ronnuille
essive		Rontuna	Rontuina
translative		Ronnuksi	Ronnuiksi
abessive		Ronnutta	Ronnuitta
instructive		—	Ronnuin
comitative		See the possessive forms below.

Possessive forms of Rontu (Kotus type 1*J/valo, nt-nn gradation)

first-person singular possessor
		singular	plural
nominative		Rontuni	Rontuni
accusative	nom.	Rontuni	Rontuni
accusative	gen.	Rontuni	Rontuni
genitive		Rontuni	Rontujeni
partitive		Rontuani	Rontujani
inessive		Ronnussani	Ronnuissani
elative		Ronnustani	Ronnuistani
illative		Rontuuni	Rontuihini
adessive		Ronnullani	Ronnuillani
ablative		Ronnultani	Ronnuiltani
allative		Ronnulleni	Ronnuilleni
essive		Rontunani	Rontuinani
translative		Ronnukseni	Ronnuikseni
abessive		Ronnuttani	Ronnuittani
instructive		—	—
comitative		—	Rontuineni

second-person singular possessor
		singular	plural
nominative		Rontusi	Rontusi
accusative	nom.	Rontusi	Rontusi
accusative	gen.	Rontusi	Rontusi
genitive		Rontusi	Rontujesi
partitive		Rontuasi	Rontujasi
inessive		Ronnussasi	Ronnuissasi
elative		Ronnustasi	Ronnuistasi
illative		Rontuusi	Rontuihisi
adessive		Ronnullasi	Ronnuillasi
ablative		Ronnultasi	Ronnuiltasi
allative		Ronnullesi	Ronnuillesi
essive		Rontunasi	Rontuinasi
translative		Ronnuksesi	Ronnuiksesi
abessive		Ronnuttasi	Ronnuittasi
instructive		—	—
comitative		—	Rontuinesi

first-person plural possessor
		singular	plural
nominative		Rontumme	Rontumme
accusative	nom.	Rontumme	Rontumme
accusative	gen.	Rontumme	Rontumme
genitive		Rontumme	Rontujemme
partitive		Rontuamme	Rontujamme
inessive		Ronnussamme	Ronnuissamme
elative		Ronnustamme	Ronnuistamme
illative		Rontuumme	Rontuihimme
adessive		Ronnullamme	Ronnuillamme
ablative		Ronnultamme	Ronnuiltamme
allative		Ronnullemme	Ronnuillemme
essive		Rontunamme	Rontuinamme
translative		Ronnuksemme	Ronnuiksemme
abessive		Ronnuttamme	Ronnuittamme
instructive		—	—
comitative		—	Rontuinemme

second-person plural possessor
		singular	plural
nominative		Rontunne	Rontunne
accusative	nom.	Rontunne	Rontunne
accusative	gen.	Rontunne	Rontunne
genitive		Rontunne	Rontujenne
partitive		Rontuanne	Rontujanne
inessive		Ronnussanne	Ronnuissanne
elative		Ronnustanne	Ronnuistanne
illative		Rontuunne	Rontuihinne
adessive		Ronnullanne	Ronnuillanne
ablative		Ronnultanne	Ronnuiltanne
allative		Ronnullenne	Ronnuillenne
essive		Rontunanne	Rontuinanne
translative		Ronnuksenne	Ronnuiksenne
abessive		Ronnuttanne	Ronnuittanne
instructive		—	—
comitative		—	Rontuinenne

Rontu is the 3952^nd (tied with 19 other surnames) most common surname in Finland, belonging to 191 individuals, according to February 2023 data from the Digital and Population Data Services Agency of Finland.