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oscuridad f. (Noun) "darkness"

13th cent. From Latin oscuritatem, accusative of obscuritas 'id.' Derived from obscurus "dark" (see oscuro).

Romance: Western Vulgar Latin: Asturian escuridá, Portuguese obscuridade, French obscurité, Italian oscurità
oscuro (Adjective) "dark"

12th cent. From Latin obscurus 'id.' From ob(s) "toward" (see ob-) and a fossil *scurus or *curus meaning "darkened." From Proto-Italic *skoi-ro- or *koi-ro- 'id.' If indeed related to Greek, Celtic and Gothic cognates, then from Proto-Indo-European *skoh2-i̯-ro- 'id.' From a root *skeh2- "to cover."

Romance: Western Vulgar Latin: Portuguese obscuro, Galician escuro, Catalan obscur, French obscur, Italian oscuro ; Eastern Vulgar Latin: Aromanian scur, Romanian obscur ; Sardinian: iscuru

Indo-European: Germanic: Gothic skeirs "bright," Old Norse skírr 'id.;' Hellenic: Ancient Greek σκίρον (skíron) "shady?"
-oso Adjective-forming suffix indicating an abundance or a bundle.

From Latin -osus, Old Latin -osos. From Proto-Italic *ōnt-to- 'id.' From Proto-Indo-European *o-u̯ont-to- 'id.'

Romance: Western Vulgar Latin: Asturian -osu, Portuguese -oso, Catalan -ós, French -eux, Italian -oso; Eastern Vulgar Latin: Aromanian -os, Romanian -os; Sardinian: -oso; Extra-Comparanda: English -ose
oso m. (Noun) "bear"

11th cent. From Latin ursus 'id.' From Proto-Italic *orsso- 'id.' From Proto-Indo-European *h2tḱo- 'id.'

Romance: Western Vulgar Latin: Asturian osu, Portuguese usso, Galician oso, Catalan ós, French ours, Italian orso ; Eastern Vulgar Latin: Aromanian ursu, Romanian urs ; Sardinian: ursu

Indo-European: Celtic: Old Irish art "bear," "hero," Middle Welsh arth "bear," Old Breton Ard-, Arth- 'id.,' Gaulish Artio "bear goddess;" Albanian: arí "bear;" Hellenic: Ancient Greek ἄρκτος (árktos) "bear;" Armenian: arǰ "bear;" Indo-Iranian: Sanskrit ŕ̥kṣa- "bear," Young Avestan arša 'id.;' Anatolian: Hittite ḫartakka- "bear"

As de Vaan (2014) points out, the word was heavily subjected to taboo distortion, as it was forbidden to speak the name of the bear during a hunt. Thus the word is phonologically warped. The appurtanance of Latin ursus is difficult to explain, Proto-Italic *orsso- should yield **orsus; furthermore, Proto-Italic *orsso- is difficult to explain because Proto-Indo-European *h2rtḱo- should yield **arsso-.
otorgar (Verb) "to authorize"

11th cent. From Vulgar Latin *auctoricare "to grant," from Latin auctorare 'id.,' derived from augere "to create," "to enlarge" (see aumento).

Romance: Western Vulgar Latin: French octroyer, Italian otriare
otro (Adjective) "other," "another"

10th cent. Old Spanish altro. 11th cent. Old Spanish otro. From Latin alter "other" but also the ordinal number "second." From Proto-Italic *āl-tero- 'id.' From Proto-Indo-European *h2el- "other" and *-tero- "one of the two," a comparative suffix (see -tr-).

Romance: Western Vulgar Latin: Asturian otru, Portuguese outro, Galician outro, Catalan altre, French autre, Italian altro ; Eastern Vulgar Latin: Aromanian altu, Romanian alt ; Sardinian: àteru

Italic: Oscan alttram "the other"

For further commentary on *h2el- see el (2), él, ella, ello.
-oy First person singular.

Old Spanish -o or . The explanation for the unexpected development from -o to -oy is unclear. The most probable theories are: contamination from yo (e.g. so yo > soy yo ; do yo > doy yo) , Müller (1963); and (2) contamination from the now-extinct word y "there," which is known to be the origin of <y> in hay "there is" (see discussion and sources in Lloyd 1987).
oyente (Noun) "auditor"

15th cent. From oír.