The only free and comprehensive online etymological dictionary of the Spanish language
genio (3) m. (Noun) "genie"

An attempt to render Arabic jinni "genie," "spirit," "demon" using an already-existing word in Spanish, genio, the physical manifestation of nature as a person or place in Roman mythology (see genio (2)).
gente f. (Noun) "people"

12th cent. Old Spanish yente. From Latin gentem, accusative of gens "clan," "household;" originally "race." From Proto-Italic *genti- 'id.' From Proto-Indo-European *ǵénh1-ti̯- 'id.' From *ǵenh1- "to birth." See also género, germen.

Romance: Western Vulgar Latin: Asturian xente, Portuguese gente, Galician xente, Catalan gent, French gens, Italian gente; Eastern Vulgar Latin: Aromanian gintã, Romanian gintă; Sardinian: gente

Indo-European: Germanic: Old Norse kind "kind," English kind; Hellenic: Ancient Greek γένεσις (génesis) "birth"
germen m. (Noun) "germ"

18th cent. learned borrowing from Latin germen "seed," "offspring." From Proto-Italic *germen 'id.' From Proto-Indo-Europen *ǵenh1-mn̥ 'id.' From *ǵenh1- "to create." See also gente, género.

Romance: Western Vulgar Latin: Portuguese germe, French germe, Italian germe; Eastern Vulgar Latin: Romanian germen
gimnasia f. (Noun) "gymnastics"

19th cent. Borrowed from Latin gymnasia "bodily exercises," borrowed from Ancient Greek γῠμνᾰ́σιᾰ (gymnásia) 'id.,' the plural of γυμνάσιον (gumnásion) "gymnasium" (see gimnasio).
gimnasio m. (Noun) "gymnasium"

17th cent. Borrowed form Latin gymnasium 'id.,' itself borrowed from Ancient Greek γυμνάσιον ‎(gumnásion) 'id.' Formed from γυμνός (gumnós) "naked," as exercises were performed nude. From Proto-Indo-European *nogw-no- 'id.' (whence nudo (1)).
gobernar (Verb) "to govern"

10th cent. From Latin gobernare "to govern," but originally "to steer a ship." Borrowed from Greek κῠβερνᾶν (kybernân) "to steer," and metaphorically "to rule." Of unknown origin. Perhaps borrowed from a non-Indo-European language.
gobierno m. (Noun) "government"

14th cent. Formed from the Latin verb gobernare "to govern," but originally "to steer a ship" (see gobernar).
golpe m. (Noun) "strike," "blow"

12th cent. Old Spanish colpe. From Late Latin colpus 'id.,' a syncopation of Latin colaphus "blow (by hand)." Borrowed from Ancient Greek κόλαφος ‎(kólaphos) "slap." Of unknown origin. Borrowed from a non-Indo-European language.
gordo (Adjective) "fat"

12th cent. From Latin gurdus "heavy," "stupid." Even as late as the 18th cent., gordo could mean dull-witted. Of unknown origin. Borrowed from a non-Indo-European language in Iberia.

Also the origin of the surnames Gordo, Gordillo, Gordilla, Gordito, Gorejo, Gordjuela, Gordón, and Gordoncillo; originally used as names for overweight individuals and later fossilized into surnames.

Romance: Western Vulgar Latin: Asturian gordu, Portuguese gordo, Catalan gord, French gourd

Gorda or perra gorda "10 cent coin," c. 1870, an uncommon name first made in reference to the 10 cent coins minted by the the provisional government of Spain of 1868-1871. The coin featured a lion with an unclear design that resembled more a fat dog than a stately lion. As the design has long since been retired, the name perra gorda has outlived the coin.

"Furthermore - returning to my original plan - words are either Latin or foreign. Foreign words, just like people, have come to us from almost every nation. ...I have heard that gurdus, the vulgar word for "fool," comes from Spain." ~ Quintilian, De institutione oratorio (in The Orator's Education 2002)
gracia f. (Noun) "grace," "favor;" (plural) "thanks"

12th cent. From Latin gratia 'id.' From gratus "pleasing" (see grado (2)).

Also the origin of the surnames Gracia and Gracián (from the Latin name Gratianus, from Gratius). As regards the origin of Gracia, a district of Barcelona, it derives from the name of a local Carmelite convent called Nostra Senyora de Gràcia in Catalan.

Romance: Western Vulgar Latin: Asturian gracia, Portuguese graça, Catalan gràcia, French grâce, Italian grazia; Eastern Vulgar Latin Romanian grație

In Roman society, grace was as much a religious as economic relief. "[Latin] gratia consists in saving expenditure. ...In a money-based civilization “grace” shown to a person is to “show grace” to him by suspending his obligation to pay for the service received. This is how a term of sentiment came to be used in an economic sense, without altogether severing itself from the religious context in which it arose." ~ E. Benveniste, Indo-European Language and Society (1973)