| AKIBA m Hebrew |
| AKIVA m Hebrew |
| BINE f Danish |
| COBA f Dutch |
| COBUS m Dutch |
| COBY m & f English |
| COOS m Dutch |
| DÍDAC m Catalan |
| DIDACUS m Medieval Spanish |
| DIEGO m Spanish |
| DIOGO m Portuguese |
| GIACHETTA f Italian |
| GIACOBBE m Italian |
| GIACOMO m Italian |
| HAGOP m Armenian |
| HAKOB m Armenian |
| HAMISH m Scottish |
| HEMI m Maori |
| IACOBUS m Biblical Latin |
| IACOMUS m Late Roman |
| IACOPO m Italian |
| IAGO m Welsh, Galician, Portuguese (Rare) |
| IAKOBOS m Biblical Greek |
| IAKOPA m Hawaiian |
| IAKOVU m Old Church Slavic |
| IB m Danish |
| JAAGUP m Estonian |
| JAAK m Estonian |
| JAAKKO m Finnish |
| JAAKOB m Estonian |
| JAAKOPPI m Finnish |
| JAAP m Dutch |
| JACI f English |
| JACKALYN f English (Rare) |
| JACKI f English |
| JACKIE m & f English |
| JACKLYN f English |
| JACLYN f English |
| JACÓ m Portuguese |
| JACOB m English, Dutch, Swedish, Norwegian, Danish, Biblical |
| JACOBA f Dutch |
| JACOBINA f Dutch |
| JACOBINE f Norwegian, Danish, Dutch |
| JACOBO m Spanish |
| JACOBUS m Dutch, Late Roman |
| JACOMINA f Dutch |
| JACOPO m Italian |
| JACQUELINE f French, English |
| JACQUELYN f English |
| JACQUES m French |
| JACQUETTA f English (British) |
| JACQUETTE f French (Rare) |
| JACQUI f English (British) |
| JAE m English (Rare) |
| JAGO m Cornish |
| JAIME (1) m Spanish, Portuguese |
| JAIME (2) f English |
| JAIMIE f English |
| JAKA m Slovene |
| JAKAB m Hungarian |
| JAKE m English |
| JAKES m Basque |
| JAKI f English (Rare) |
| JAKKI f English (Rare) |
| JÁKOB m Hungarian |
| JAKOB m German, Swedish, Norwegian, Danish, Dutch, Slovene, Estonian, Croatian |
| JAKOV m Croatian, Macedonian |
| JAKŠA m Croatian |
| JAKUB m Polish, Czech, Slovak |
| JAMES m English, Biblical |
| JAMESINA f Scottish |
| JAMEY m English |
| JAMI f English |
| JAMIE m & f Scottish, English |
| JAMISON m English |
| JAPIK m Frisian |
| JAQUELINE f English (Modern) |
| JAQUELYN f English (Rare) |
| JAŠA m Slovene |
| JASKA m Finnish |
| JAUME m Catalan |
| JAUMET m Catalan |
| JAY (1) m English |
| JAYCOB m English (Rare) |
| JAYE f English |
| JAYLA f English (Modern) |
| JAYLEE f English (Modern) |
| JAYLEN m & f African American (Modern), English (Modern) |
| JAYLENE f English (Modern) |
| JAYLIN m & f African American (Modern), English (Modern) |
| JAYLYN f English (Modern) |
| JAYMA f English (Rare) |
| JAYME f English |
| JAYMES m English (Modern) |
| JEB m English |
| JEM m English (Archaic) |
| JEMMY m English (Archaic) |
| JEPPE m Danish |
| JIM m English |
| JIMI m English |
| JIMMIE m & f English |
| JIMMY m English |
| JOKŪBAS m Lithuanian |
| KAPEL m Yiddish |
| KIMO m Hawaiian |
| KOBUS m Dutch |
| KOBY m English (Modern) |
| KOOS m Dutch |
| KOPPEL m Yiddish |
| KUBA m Polish |
| LAPO m Italian |
| SANTIAGO m Spanish, Portuguese |
| SÉAMAS m Irish |
| SÉAMUS m Irish |
| SEUMAS m Scottish |
| SHAMUS m Irish |
| SHEAMUS m Irish |
| SJAAK m Dutch |
| SJAKIE m Dutch |
| THIAGO m Portuguese (Brazilian) |
| TIAGO m Portuguese |
| XANTI m Basque |
| YAAKOV m Hebrew, Biblical Hebrew |
| YAGO m Spanish |
| YAKIV m Ukrainian |
| YAKOV m Hebrew, Russian, Bulgarian |
| YAKUB m Arabic |
| YAKUP m Turkish |
| YANKEL m Yiddish |
| YAQUB m Arabic |
| YASHA m Russian |
| ŽAKLINA f Croatian |
| ŻAKLINA f Polish |
| ZHAKLINA f Macedonian, Bulgarian |
