The only free and comprehensive online etymological dictionary of the Spanish language
-ía Feminine noun-forming prefix.

From Latin -ia 'id.' From Proto-Italic *-ia 'id.' From Proto-Indo-European *-i̯h2 'id.' The ending *-h2 originally functioned by creating collective nouns, see -a.

Romance: Western Vulgar Latin: Asturian -ariu, Portuguese -ia, Galician -ía, Catalan -ia, French -ie, Italian -ia; Eastern Vulgar Latin: Romanian -ie

Indo-European: Hellenic: Ancient Greek -ία (-ía)
-ico Adjective-forming suffix

From Latin -icus 'id.' From Proto-Italic *-īko-. A decausative from the instrumental: Proto-Indo-European *-i̯h1-ko- 'id.'

Also an uncommon variant -eco reflects the i ~ e confusion in Vulgar Latin in Iberia.

Romance: Western Vulgar Latin: Asturian -icu, Portuguese -ico, Galician -ico, Catalan -ic, French -ique, Italian -ico; Eastern Vulgar Latin: Aromanian -ic; Extra-Comparanda: English -ic (borrowed from French -ique)

Indo-European: Balto-Slavic: Old Church Slavonic -ъkъ; Hellenic: Ancient Greek -ικός (ikós); Indo-Iranian: Sanskrit -śas
idea f. (Noun) "idea"

15th cent. From Latin idea 'id.,' from Greek ἰδέα (idéa) "appearance," "form." From Proto-Indo-European *u̯ei̯d- "to see," "to know." See also ver.

Romance: Western Vulgar Latin: Asturian idea, Portuguese ideia, Catalan idea, French idée, Italian idea ; Eastern Vulgar Latin: Romanian idee
idiota (Adjective, Noun) "idiotic;" "idiot"

13th cent. From Latin idiota 'id.,' borrowed from Greek ἰδιώτης (idiótes) "uneducated person," "commoner." From ἴδιος (ídios) "private." From Proto-Indo-European *su̯o-i̯o- "ourself." Developed from the reflexive pronoun *su̯e- (see se (1)).
-ido Adjective-forming suffix indicating a tendency.

From Latin -idus 'id.' From Proto-Italic *-idos 'id.' From Proto-Indo-European *-i̯-dho- 'id.' An i-stem adjective to form an adjective from verbs.

Romance: Western Vulgar Latin: Asturian -íu, Portuguese -ido, French -ide, Italian -ido; Eastern Vulgar Latin: Romanian -ed
-igar Suffix indicating action or doing.

From Latin agere "to do," "to drive." From Proto-Italic *ag-e/o- 'id.' From Proto-Indo-European *h2eǵ-e/o- 'id.' A thematic present.

Italic: Oscan acum "to act," Marrucinian agine "through the act"

Indo-European: Celtic: Old Irish aig "to drive," Old Welsh hegit "goes;" Germanic: Old Icelandic aka "to drive;" Hellenic: Ancient Greek ἄγ- (ág) "to drive;" Armenian: acem 'id.' Indo-Iranian: Sanskrit ájati "drives," Young Avestan azaiti 'id.;' Tocharian: A āk- "to lead," B āk- 'id.'
iglesia f. (Noun) "church"

10th cent. From Vulgar Latin eclesia 'id.,' from Latin ecclesia "assembly." Borrowed from Greek ἐκκλησία (ekklesía) "assembly" (more literally "those called out") composed of ἐκ (ek) "out" and κᾰλεῖν (kaleîn) "to call."

Also the origin of the surnames de la Iglesia, Igreja, Igrejas, Iglesias, Esclesies, and Laiglesia.

Romance: Western Vulgar Latin: Asturian eglesia, Portuguese igreja, Galician igrexa, Catalan església, French église, Italian chiese; Sardinian: chegia

Greek ἐκ (ek) "out" is cognate to Latin ex (Spanish ex) and κᾰλεῖν (kaleîn) "to call" is cognate to Latin clamare "to call" (Spanish llamar). Thus, the Greek word ἐκκλησία "assembly" has a direct twin in Latin exclamare "to exclaim" (Spanish exclamar).
ignorar (Verb) "to ignore"

15th cent. Borrowed from Latin ignorare "to not know." From Proto-Italic *en-gnōs-e/o- 'id.' From *en-, a negation prefix (see in-), and *gnōs-e/o- "to know." From Proto-Indo-European *ǵneh3-s- 'id.'

Romance: Western Vulgar Latin: Asturian inorar, Portuguese ignorar, Catalan ignorar, French ignorer, Italian ignorare ; Eastern Vulgar Latin: Romanian ignora

Indo-European: Indo-Iranian: Sanskrit jānati "he recognizes;" Tocharian: A kñasäṣt "you recognize;" Anatolian: Hittite kane-zi "to recognize"
igual (Adjective) "equal"

Very early 12th cent. Old Spanish egual. From Latin æqualis 'id.,' composed of æquus "equal" and -alis, an adjective-forming suffix indicating a relationship (see -al (2)). Latin æquus is of unknown origin.

Romance: Western Vulgar Latin: Asturian igual, Portuguese igual, Galician igual, Catalan igual, French égal, Italian uguale; Eastern Vulgar Latin: Romanian egal; Sardinian: aguale
-il Adjective-forming suffix indicating a relation.

From Latin -ilis. From Proto-Italic *-īlis 'id.' From Proto-Indo-European *-i̯h2-li̯- 'id.' An i-stem with an adjectival extension.

Romance: Western Vulgar Latin: Asturian -il, Portuguese -il, Galician -il, Catalan -il, French -ile, Italian -ile; Eastern Vulgar Latin: Aromanian -ilji, Romanian -il