The only free and comprehensive online etymological dictionary of the Spanish language
gana f. (Noun) "desire"

Likely conserving a now-archaic sense of ganar meaning "to covet" or "to desire."
ganado (1) (Adjective) "earned"

10th cent. From ganar.
ganado (2) m. (Noun) "herd," "livestock," "cattle"

12th cent. Developed from a sense of earnings or won wealth, especially prevalent in antiquity when ganar likely meant to win spoils or booty. From ganado (1).
ganar (Verb) "to win," "to gain"

10th cent. According to RAE and Corominas (1983) putatively from an unattested Gothic word *ganan "to covet;" or according to Roberts (2014), from Gothic *ganô "eagerness." I am yet to find supporters among Germanicists for these theories.
gato (Noun) "cat"

10th cent. From Late Latin cattus 'id.' The voicing of Latin /k/ to Spanish /g/ is unexplained. Borrowed from an Afro-Asiatic source (compare Coptic klít "cat").

Listed by Tibón (1988) as a particularly ancient nickname for physically-gifted individuals who showed agility and reflexes like a cat; then later it fossilized into the surnames Gato, Gatón, and Gata.

Romance: Western Vulgar Latin: Asturian gatu, Portuguese gato, Galician gato, Catalan gat, French chat, Italian gatto; Eastern Vulgar Latin: Aromanian cãtushe, Romanian cătușă; Sardinian: batu

The shound shift of /k/ to /g/ did not affect c-initial words in Latin, so we are left with the question of whence the g- in gato? Considering cognates in Catalan gat and Italian gatto, we could reconstruct a Vulgar Latin variant *gattus but this looks unmotivated. A loan from another language into Spanish is phonologically fine, but at odds with the historical record.
general (Adjective, Noun) "general;" (f.) "general's wife"

13th cent. From Latin generalis 'id.' From genus "class (of people)," "birth" (see género for further etymology) with adjective-forming suffix -alis (see -al (2)).

The use of generala to indicate "general's wife" instead of "general" is due to the profession of general being exclusive to men. Only recently may the feminized word refer to a general.

Romance: Western Vulgar Latin: Portuguese general, Catalan general, French général, Italian generale; Eastern Vulgar Latin: Romanian general
género m. (Noun) "kind," "genus"

14th cent. From Latin genus 'id.' From Proto-Italic *gen- "race," "offspring." From Proto-Indo-European *ǵenh1- 'id.,' but likely originally a verb "to birth." See also gente, germen.

Romance: Western Vulgar Latin: Portuguese gênero, French genre, Italian genere; Eastern Vulgar Latin: Romanian gen

Indo-European: Celtic: Gaulish Cintu-genus "firstborn," Old Irish Éogan, 2nd/3rd cent. king of Munster, Old Welsh Morgen "sea-born" (not related to the modern Welsh name Morgan, from Old Welsh Morcanth), Old Breton gen "race;" Hellenic: Ancient Greek γένος (génos) "race;" Armenian: cin "birth;" Indo-Iranian: Sanskrit jánas- "race"
genial (Adjective) "brilliant," "great"

From Latin genialis "marital," but also "festive." From genius "guardian spirit" and -alis (see genio (2) and -al (2) respectively).

Romance: Western Vulgar Latin: Portuguese genial, Catalan genial, French génial, Italian geniale
genio (1) m. (Noun) "temper;" "genius"

Originally meaning "personality" (16th cent.). The modern meanings date to the 19th cent. From Latin genius "wit," "talent." Earlier meaning was as a source of strength, and before that as the spirit of a people - which begat a second meaning in Latin of a guardian spirit (see genio (2). From gens "clan," "household" (see gente).

Romance: Western Vulgar Latin: Portuguese génio, Catalan geni, French génie, Italian genio; Eastern Vulgar Latin: Romanian geniu
genio (2) m. (Noun) "Genius;" "angel," "divine figure"

From Latin genius "guardian spirit." The modern sense of genio as a divine figure is taken from artistic representations of the Roman genius in art. Earlier meaning a source of strength, before that the spirit of a people - which begat a second meaning in Latin of a guardian spirit (see quote below). From gens "clan," "household" (see gente).

"The worship of the Genius [the guardian spirit] was a remarkable part of the religion of the Romans; they having derived it from the Tuscans, in whose system it formed a prominent feature. The word Genius is evidently a translation of a Tuscan term, signifying Generator, and the Genius was therefore viewed as a deity who had the power of producing...

When a local genius made himself visible, he appeared in the form of a serpent, that is, the symbol of renovation, or of new life. In works of art, the genii are usually represented as winged beings; an on Roman monuments, a genius usually appears as a youth dressed in toga, with a patera or cornucopia in his hand, and having his head covered. The genius of a place is represented in the form of a serpent eating fruit placed before him." M. A. Dwight, Grecian and Roman Mythology (1849)