The only free and comprehensive online etymological dictionary of the Spanish language
ya (Adverb) "now," "already"
Very early 12th cent. From Latin iam 'id.' From Proto-Italic *iām "as far as this is concerned." From Proto-Indo-European *h1i̯-h2m "this," in the accusative case. Probably from *īm "he," "she;" the *h2 added via analogy with other pronouns.
Romance: Western Vulgar Latin: Asturian , Portuguese , Galician xa, Catalan ja, French , Italian già
y, e (Conjunction) "and"
10th cent. Old Spanish e, uncommon hi, i. From Latin et 'id.,' a word in competition with suffix -que of the same meaning. Proto-Italic *eti 'id.' From Proto-Indo-European *h1eti̯ "still," "also."
Romance: Western Vulgar Latin: Asturian y, Portuguese e, Galician e, Catalan i, French et, Italian e; Eastern Vulgar Latin: Aromanian e, Romanian e; Sardinian: e
Italic: Umbrian et 'id.,' Paelignian et 'id.'
Indo-European: Celtic: Gaulish eti "yet," Old Breton et- 'id.;' Germanic: Gothic "but;"Hellenic: Ancient Greek ἔτι (hépi) "still;" Indo-Iranian: Sanskrit áti "beyond," Avestan aiti 'id.'
Following de Vaan (2014), in Proto-Indo-European and later, the word meant "furthermore" to coordinate an additional phrase onto a previous statement while the language used the suffix *-kwe (Latin -que; not in Spanish). Eventually the *-h1et overshadowed and finally replaced the suffix.
yesca f. (Noun) "tinder"
13th cent. From Vulgar Latin *esca "kindling." From Latin esca "food," from esse "to eat." From Proto-Italic *ed- "to eat" (see note under comer for a continuing etymology).
Romance: Western Vulgar Latin: Asturian yesca, Portuguese isca, Galician esca, Catalan esca, French esche, Italian esca; Eastern Vulgar Latin: Aromanian eascã, Romanian iască
Italic: Oscan edum "to eat"
Indo-European: Celtic: Old Irish ithid "to eat;" Germanic: Gothic itan "to eat," Old Norse eta 'id.,' Old High German ezzan 'id.,' Old Saxon etan 'id.,' Old English etan 'id.' (English to eat); Balto-Slavic: Old Church Slavonic jasti "to eat," Russian est' 'id.,' Czech jísti 'id.,' Polish jeść 'id.,' Slovene jẹ́sti 'id.,' Old Prussian īst 'id.,' Lithuanian ė́sti 'id.,' Latvian êst 'id.;' Hellenic: Ancient Greek ἔδειν (édein) "to eat;" Armenian: owtem "to eat;" Indo-Iranian: Sanskrit ádmi "I eat;" Tocharian: A nätsw- "to starve," B mätsts- 'id.;' Anatolian: Hittite ed-zi "to eat," Cuneiform Luwian ād- 'id.,' Palaic ad- 'id.'
yo (Personal Pronoun) "I"
10th cent. From Vulgar Latin eo, from Latin ego 'id.' From Proto-Italic *egō 'id.' From Proto-Indo-European *h1eǵ-(o)H. From earlier *h1eǵ- 'id.'
Romance: Western Vulgar Latin: Asturian yo, Portuguse eu, Galician eu, Catalan jo, French je, Italian io; Eastern Vulgar Latin: Aromanian io, Romanian eu; Sardinian: eo
Indubitably, the word is especially ancient in Proto-Indo-European, at one point even labelled a "Devonion rock" of the language by Benjamin Fortson (2011). Because of its extreme age, the semantic sense of *h1eǵ- and its many suffixes (Latin points to *-(o)H; Sanskrit to *-om; Germanic *-Hom; and Hittite to a word without a suffix) have inspired significant discussion (see Sihler 2008).
yugo m. (Noun) "yoke"
13th cent. Old Spanish yugo, iuuo. Borrowed from Latin iugum 'id.' From Proto-Italic *jugo- 'id.' From Proto-Indo-European *i̯ug-o- "yoke," but more literally "joined together." From the root *i̯eu̯g- "to yoke together."
Variants: Almerían huvo, Old Spanish iuuo
Romance: Western Vulgar Latin: Asturian xugu, Portuguese jugo, Galician xugo, Catalan jou, French joug, Italian giogo; Eastern Vulgar Latin: Aromanian chubo, Romanian jug; Sardinian: giú
Indo-European: Celtic: Old Irish cuing "yoke," Middle Welsh iou 'id.,' Middle Breton yeu 'id.,' Cornish ieu 'id.;' Germanic: Gothic juk "yoke," Old Norse ok 'id.,' Old High German joh 'id.,' Old Saxon juk 'id.,' Old English geoc 'id.' (English yoke); Balto-Slavic: Old Church Slavonic igo "yoke," Russian ígo 'id.,' Czech jho 'id.,' Polish jugo 'id.,' Slovene igọ̑ 'id.,' Lithuanian jùngas 'id.,' Latvian jûgs 'id.;' Indo-Iranian: Sanskrit yúj- "ally," Young Avestan yuiiō- "yoke;" Anatolian: Hittite iūk- "yoke," Cuneiform Luwian Lycian 'id.'
Myriad written attestation in Spanish and in Romance languages affirm that this is not a learned borrowing from Latin, yet Corominas (1991) notes that we should expect **jogo from iugum, and not yugo. Preservation of yu- could be from Leonese influence.

Old Spanish iuuo (early 13th cent.), however surprising, cannot be dismissed as a writing error: in the Almerían dialect we find a modern reflex in huvo. This must be a continuation of Vulgar Latin *iuum.
The ability to reconstruct a word for yoke in Proto-Indo-European proves that the ancient Indo-Europeans had draft animals used to pull wheeled carts.