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incluso (Adjective, Adverb) "enclosed;" "including"

From Latin inclusus 'id.,' the past participle of includere "to enclose." From in- and claudere "to close" (see en- and clausurar).
increíble (Adjective) "incredible"

From in- "not" and creíble "believable."
infierno m. (Noun) "hell;" "inferno"

12th cent. From Latin infernus 'id.,' but originally "of the lower region," from inferus "low." From Proto-Italic *enþero- 'id.' From Proto-Indo-European *n̥dher-o- 'id.' From *n̥dhér- "under."

Romance: Western Vulgar Latin: Asturian infiernu, Portuguese inferno, Galician inferno, Catalan infern, French enfer, Italian inferno; Eastern Vulgar Latin: Romanian infern; Sardinian: iferru

Italic: Faliscan ifra "beneath"

Indo-European: Celtic: Gaulish anderon "of the gods of the underworld;" Germanic: Gothic undar "under," Old Norse undir 'id.,' Old High German untar "below," Old Saxon undar "under," Old English under; Indo-Iranian: Sanskrit ádhara- "lower," Young Avestan aδara- 'id.'
información f. (Noun) "information"

14th cent. From Latin informatio "formation;" "education" from informare "to inform" (see informar).

Romance: Western Vulgar Latin: Portuguese informação, Galician información, Catalan informació, Italian informazione; Eastern Vulgar Latin:nformație
informar (Verb) "to inform"

15th cent. From Latin informare 'id.,' from in- (see en-) and formare "to form" (see formar).

Romance: Western Vulgar Latin: Portuguese informar, French informer, Italian informare
Inglaterra f. (Noun) "England"

From inglés and -terra "earth."
inglés (Adjective, Noun) "English;" "English person"

From Middle English Inglis "English" with the ending -is analogous to the native noun-forming suffix -és.

Also the origin of the surname Inglés, given to immigrants from England.
iniciar (Verb) "to begin"

18th cent. From Latin initiare 'id.' From initium "beginning" (see inicio).

Romance: Western Vulgar Latin: Portuguese iniciar, Galician iniciar, Catalan iniciar, French initier, Italian iniziare
inicio m. (Noun) "beginning"

20th cent. From Latin initium 'id.' From inire "to go into." From in- "in" (see en-) and ire "to go" (see ir).

Romance: Western Vulgar Latin: Portuguese início, Catalan inici, Italian inizio
inmediatamente (Adverb) "immediately"

From inmediato and -mente, an adverb-forming suffix.