The only free and comprehensive online etymological dictionary of the Spanish language
ocio m. (Noun) "free time"

15th cent. From Latin otium "leisure." Of unknown origin.

Romance: Western Vulgar Latin: Portuguese ócio, Catalan oci, Italian ozio
ocupado (Adjective) "occupied"

From ocupar.
ocupar (Verb) "to occupy"

15th cent. From Latin occupare 'id.' From ob- "toward" (see o-) and capere "to capture."

Romance: Western Vulgar Latin: Portuguese ocupar, Catalan ocupar, French occuper, Italian occupare ; Eastern Vulgar Latin: Aromanian apuc, Romanian apuca
ocurrir (Verb) "to occur"

From Latin occurrere "to run to," "to attack." From ob- "toward" (see o-) and currere "to run" (see correr).

Romance: Western Vulgar Latin: Portuguese ocorrer, Italian occorrere
odiar (Verb) "to hate"

17th cent. From Latin odiare 'id.,' a verb formed from odium "hate" (see odio (1)).
odio (1) m. (Noun) "hatred"

13th cent. An uncommon word until the 15th cent. From Latin odium 'id.' From Proto-Italic *odio- 'id.' From Proto-Indo-European *h3od-i̯o- 'id.' From an ancient verbal root *h3ed- "to hate."

Romance: Western Vulgar Latin: Portuguese ódio, Catalan odi, Italian odio ; Sardinian: odiu

Indo-European: Germanic: Old Norse etja "to incite," Old High German an-azzen 'id.,' Old English atol "terrible;" Hellenic: Ancient Greek ὀδύσασθαι (odysasthai) "to be angry;" Armenian: ateam "to hate"
Odio (2) (Surname)

From Basque odio "in the ravine," from odi "ravine" and the locative suffix -o. Trask (2008) echoes Michelena's Apellidos vascos (1973) by tentatively suggesting an origin in Latin fodina "mine."
oeste m. (Noun) "west"

Late 15th cent. Old Spanish oüeste. Borrowed from French oeste 'id.,' itself borrowed from a Germanic source (compare English west). From Proto-Germanic *westera- "west," "western." The first element *wes- is of uncertain etymology, probably *u̯e-kwsp- "evening;" the second element *-tera- is a comparative suffix used in directions from Proto-Indo-European *-tero- (see -tr-).

Romance: Western Vulgar Latin: Galician oeste, Catalan oest, French ouest, Italian ovest

Italic: Latin vesper "evening"

Germanic: North Germanic: Old Norse vestr "west;" West Germanic: Old High German westar "west," Old Saxon westar 'id.,' English west

Indo-European: Celtic: Old Irish fescor "evening," Middle Welsh uch 'id.;' Balto-Slavic: Old Church Slavonic večerъ "evening," Russian véčer 'id.,' Czech večer 'id.,' Polish wieczór 'id.,' Slovene večę̑r 'id.,' Lithuanian vãkaras, Latvian vakars 'id.;' Hellenic: Ancient Greek ἕσπερος (ésperos) "evening;" Armenian: gišer "night;" Indo-Iranian: Sanskrit kṣáp- "night," Young Avestan xšap- 'id.;' Anatolian: Hittite išpant- "night"
oficial (Adjective, Noun) "official," "officer"

15th cent. Borrowed from Late Latin officialis 'id.,' but originally an office attendent. From officium "office," "duty" (see oficio).
oficina f. (Noun) "office"

Very early 17th cent. From Latin officina 'id.,' from opificina "workshop." Formed from opi- "power to help," -ficio "maker," and -ina, a diminutive suffix. See op- and -fico respectively.

Romance: Western Vulgar Latin: Portuguese oficina, Galician oficina, Catalan oficina, Italian officina