The only free and comprehensive online etymological dictionary of the Spanish language
joto, jota (3) m. & f. (Noun) (playing card) "joker," "jack;" "male homosexual"
Of unknown origin. Consider also jote.
joven (Noun) "youth"
13th cent. From Latin iuvenis 'id.' From Proto-Italic *juwen- 'id.' From Proto-Indo-European *h2i̯u̯-h1en- "young," but more literally "one full of life's energy." From *h1oi̯-u̯- "lifetime" (see evo).
Also the origin of the surname Joven, sometimes indicating the person was under the age of 25.
Indo-European
Romance
Asturian xoven, Portuguese jovem, Galician xove, Catalan jove, French jeune, Italian giovane, Aromanian gioni, Romanian june, Sardinian giovanu
Celtic
Old Irish óetiu "youth"
Germanic
Gothic jund- "youth," Old High German jugund 'id.,' Old Saxon juguth, Old English geogoð (English youth)
Balto-Slavic
Old Church Slavonic junъ "young," Lithuanian jáunas 'id.'
Indo-Iranian
Sanskrit yúvan- "youth," Young Avestan yuuānəm 'id.'
juego m. (Noun) "game"
12th cent. From Latin iocus "joke," "game." From Proto-Italic *joko- 'id.' From Proto-Indo-European *i̯ok-o- "word."
Indo-European
Romance
Asturian xuegu, Portuguese jogo, Galician xogo, Catalan joc, French jeu, Italian gioco, Aromanian gioc, Romanian joc, Sardinian giogu
Italic
Umbrian iuca "prayers," Paelignian iocatin "to command"
Celtic
Middle Irish icht "people," Middle Welsh ieith "language," Breton yezh 'id.'
Germanic
Old High German jiht "confession"
juez (Noun) "judge"
12th cent. Old Spanish júdez, júez. From Latin iudex "judge," but more literally "law-saying." From Proto-Italic *jows-diks 'id.' From *jowo- "law" (see jurar) and *diḱ- "saying" (see -ez).
Competing feminine forms la juez / la jueza is from uncertainty due to the recent inclusion of women into the predominantly male profession. More recently, la juez has come to mean "female judge" while la jueza retains the older meaning of "judge's wife." The sense of a wife's judge is from a pre-21st cent. idea that only men could serve as judges. Also the origin of the surname Juez.
Indo-European
Romance
Asturian xuez, Portuguese juiz, Galician xuíz, Catalan jutge, French juge, Italian giudice, Romanian jude, Sardinian giuge
"The Latin compound iu-dex implies the notion of showing with authority... The whole history of Lat. dicere highlights a mechanism of authority: only the judge can dicere ius." ~ E. Benveniste, Indo-European Language and Society (1973)
jugar (Verb) "to play (a game)"
12th cent. From Vulgar Latin iocare 'id.,' from Latin iocari "to joke." Derived from the noun iocus "joke" (see juego).
Indo-European
Romance
Asturian xugar, Portuguese jogar, Galician xogar, Catalan jugar, French jouer, Italian giocare, Aromanian gioc, Romanian juca, Sardinian giocae
juicio m. (Noun) "judgement"
12th cent. From Latin iudicium 'id.,' from iudex "judge" (see juez).
Indo-European
Romance
Asturian xuiciu, Portuguese juízo, Catalan judici, Italian giudicio, Aromanian giudets, Romanian județ, Sardinian giudísciu
julio (1) m. (Noun) "July"
13th cent. From Latin Iulius 'id.,' taken from the name of Julius Caesar in honor of his birth month. Iulius was not Julius Caesar's first name but his clan name. Of uncertain origin. According to Pokorny (1959), from an unattested Old Latin form *Iovilios "Jove's;" a clan name expressing special attention to the deity Jove.
Indo-European
Romance
Portuguese julho, Galician xullo, Catalan juliol, French julliet, Italian luglio
julio (2) m. (Noun) "joule"
19th cent. Borrowed from English joule 'id.,' a unit of measurement of energy from the surname of a physicist, James Joule, who studied the nature of heat and the properties energy.
Julio (3) m. (Personal Name) "Julius"
From Latin Iulius 'id.,' taken from the name of Julius Caesar. Iulius was not Julius Caesar's first name but his clan name. See julio (1) for a continuing etymology.
junio m. (Noun) "June"
Early 13th cent. From Latin Iunius "of June," named after the goddess Iuno "Juno" (see Juno).
Indo-European
Romance
Asturian xunu, Galician xuño, Portuguese junho, Catalan juny, French juin, Romanian iunie