The only free and comprehensive online etymological dictionary of the Spanish language
ojalá (Interjection) "God willing!"
Very late 15th cent. Old Spanish oxalá. Borrowed from an Arabic phrase wa-šā’ allāh "may God will it."
Indo-European
Romance
Portuguese oxalá
ojo m. (Noun) "eye;" "source"
12th cent. From Vulgar Latin oclus 'id.' From Latin oculus 'id.' From Proto-Italic *okelo- 'id.' From Proto-Indo-European *h3okw- "eye." Probably from an older root verb *h3ekw- "to see."
Indo-European
Romance
Portuguese óculo, Catalan òcul
Germanic
Gothic augo "eye," Old Norse auga 'id.,' Old High German ouga 'id.,' Old Saxon ōga, Old English ēage 'id.' (English eye)
Albanian
Albanian sy "eye"
Balto-Slavic
Old Church Slavonic oko "eye," Russian (archaic) óko 'id.,' Czech oko 'id.,' Polish oko 'id.,' Slovene okọ̑ 'id.,' Old Prussian ackis "eyes," Lithuanian akìs "eye," Latvian acs 'id.'
Hellenic
Ancient Greek ὤψ (óps) "eye"
Armenian
Armenian akn "eye"
Indo-Iranian
Sanskrit akṣ-ī́ "eyes," Young Avestan aši "eyes"
Tocharian
A ak "eye," B ek 'id.'
In the 3rd or 4th cent. text Appendix Probi we find the line: oculus non oclus "[the word for 'eye' is] oculus, not oclus." The author's spelling correction proves how the word was pronounced by common speakers, and offers a rare glimpse of the evolution of Latin into Romance languages such as Spanish.
ok, okei (Interjection) "okay"
Borrowed from English okay, earlier OK, of unknown origin. The most popular theory is that it derives from oll korrect, a comical misspelling of "all correct," as part of an 1830s American fad of exotic abbreviations (see Read 1964).
oler (Verb) "to smell"
13th cent. From Latin olere 'id.' From Proto-Italic *od-e/o- 'id.' From Proto-Indo-European *h3ed- 'id.'
Indo-European
Romance
Asturian goler, Italian olire
Balto-Slavic
Old Czech jadati "to investigate," Lithuanian úosti "to smell," Latvian uôst 'id.'
Hellenic
Ancient Greek ὀδμή (odmé) "smell"
Armenian
Armenian hot "smell"
olor m. (Noun) "smell"
13th cent. From Latin olor 'id.,' derived from olere "to smell" (see oler).
Indo-European
Romance
Asturian golor, Catalan olor
olvidado (Adjective) "forgotten"
From olvidar.
olvidar (Verb) "to forget"
12th cent. From Vulgar Latin *oblitare 'id.,' from Latin oblivisci of the same meaning. Of unknown origin. The first element *ob looks suspiciously like the prefix *ob- "toward" (see ob-), but we are left with the puzzle in the rest of the word.
Indo-European
Romance
Asturian olvidar, Catalan oblidar, Frech oublier, Italian obliare, Aromanian ultu, Romanian uita, Sardinian olvidare
-on, -ón Augmentative suffix akin to "large."
From Vulgar Latin *-one 'id.' Of unknown origin. It is phonologically possible that it comes from Latin -onem, the accusative of -o, a suffix forming masculine nouns, however this is semantically difficult. If from Latin -o, then from Proto-Italic *-ōn- 'id.' From Proto-Indo-European *h3onh2- 'id.'
Indo-European
Romance
Portuguese -ão
opción f. (Noun) "option"
18th cent. From Latin optionem, accusative of optio 'id.' From a hypothetical verb *opere "to choose." See optar for more information.
Indo-European
Romance
Portuguese opção, French option, Italian opzione, Romanian opțiune
operación f. (Noun) "operation"
15th cent. From Latin operationem, accusative of operatio 'id.' Ultimately from operari "to operate" (see operar).
Indo-European
Romance
French opération