These names are from a list of 6000 names given to Finnish children (aged 1 to 10 years old). Some of the names may seem ordinary to Anglophones, but in Finland they're still considered rare and/or unique.
Jaajo
Jaako
JaakoppiJaani
Jaan-Marcus
Jaanu
Jaaro / Jaro
JackJacksonJacob /
Jakob /
JakubJacquesJaelJahim
Jahvetti
JakeJakiJakke
Jali
Jalle
Jalmar
JalmariJaloJamJamalJamesJamiJamieJami-Eemil
Jamiel
JanJan-Andre
Jan-Edward
Jan-Eemil
Jan-Eliel
Jan-Emil
Jan-Eric
Jan-Erik
Janiel
Jani-Petteri
Janis-Paul
Jan-Jalmar
Jan-Jarek
Jan-Joel
Jan-Kristian
Jan-Matias
Jan-Mikael
Jannu
JanosJanric
Janrik
Jan-Silver
Janttu
JanusJare
JaredJarel
Jare-Pekka
Jaret
Jarkki
Jarko
JarlJaronJaroslavJarre / Járre
JaskaJaso
JasonJasperJasperi
Jasse
Jasu
Jasu-Matias
Jawad
JaydenJaysonJeeli
Jeemi
Jeemias
Jeffery /
JeffreyJekabs
Jekki
Jelim
JemJemi
Jenns /
JensJenrik
Jeorg
JeppeJere-Antero
Jere-Jochen
Jere-Kristian
Jere-Matti
Jeremi /
JeremyJeremia
JeremiasJere-Santeri
JeriJeriko
Jerkko /
JerkoJermi
Jermu
Jero
JeromeJerri /
JerryJerry-Pekka
Jeru
JesperJesperi
Jesse-Justus
Jesse-Kasperi
Jesse-Kristian
Jeter
Jethro / Jetro
Jhordan
Jicke
Jico / Jiko
JimJimias
Jimi-Joonas
Jimi-Matias
Jimi-Oskari
Jimi-Petteri
Jimi-Rasmus
Jimmy / Jimy
Jino
Jirco-Rico
JiriJirka
Jirko
JiroJiroel
Jiska
Joa / Joah / Jooa
Joachim / Joacim / Joackim / Joahcim /
JoakimJoar
Joas / Jooas
Joda
JoeJóel / Jooel
Joel-Eemeli
Joeli
Joel-Oscar
Johán /
JohannJohan-Antti
Johan-Otto
Johan-Samuel
JohnJohnathan-John
Johnny / Johny / Jonni /
JonnyJoisa
Jomar
Jomi
JonJona /
Jonà /
JonahJonasJonatan /
Jonathan / Joonathan
JoneJones
Joni-Anssi
Joni-Oskari
Jonne
Jonne-Emil
Jonne-Kristian
Jon-Nilsa
Jonni-Pekka
Jonte
Joona-Aleksi
Joona-Julius
Joopi
Joosa / Josa
Joose /
JoseJoosef /
Joosep /
JosefJooseppiJoosu
Joosua / Josua
Jore
Josi
Josia
JoskaJosua-Simeoni
Jouka
Jouna
Jouni-Ante
Jousia
JovianJovnna
JuanJudaJuha-Iikka
Juha-Markus
Juha-Matti
JuhanJuhanaJuhanes
Juhan-Henrik
Juha-Pekka
Juha-Veikko
Juho-Antti
Juho-Eemil
Juho-Eevert
Juho-Kusti
Juho-Matti
Juho-Oskari
Juhopekka
Juho-Pekka
Juho-Petteri
Juho-Santeri
Juho-Veli
Juho-Ville
Juke
Juki
Jukko
JulianJulias
Julius-Lukas
Julle
JunaydJuniusJunnu
JunoJuri
Jusa / Jussa
Juska
Jussa Mikkal
Jussipekka
Jussu / Jusu
JustinJustusJuuse
Juuso-Matias
Jymy - means "thumping" and "rumble" in Finnish
Jyri-Peeter
Jyry - means "rumble" and "thunder" in Finnish
Jyry-Sisu - sisu means "willpower" and "vigor" in Finnish
Jysky - derived from a Finnish word "jyske" meaning "thumping"
Jörö - means "grumpy" and "sullen" in Finnish; also Grumpy the dwarf's (from Snow White and the Seven Dwarfs) Finnish name