The only free and comprehensive online etymological dictionary of the Spanish language
accidente m. (Noun) "accident"

14th cent. From Latin accidentem, accusative of accidens 'id.,' a noun from the verb accidere "to happen," "to befall." From ad- "toward" (see a(d)-) and cadere "to fall" (see caer).

The original sense of "to happen" is better preserved in the phrase por accidente "by chance," "coincidentally," and when used to describe the Christian eucharist (e.g. los accidentes del pan y vino "the qualities of the bread and wine").

Romance: Old French accident
acción f. (Noun) "action"

Late 15th cent. From Latin actionem, accusative of actio 'id.' From Proto-Italic *ak-ti- 'id.,' derived from *ag-e/o- "to act" (see -igar).

Romance: Western Vulgar Latin: Asturian aición, Portuguese ação, Catalan acció, French action, Italian azione; Eastern Vulgar Latin: Romanian acțiune

Italic: Umbrian ahti-
aceptar (Verb) "to accept"

13th cent. Old Spanish acetar. From Latin acceptare 'id.,' from accipere 'id.' and frequentive suffix -tare (see note under faltar). From ad- "toward" and capere "to take" (see caber).

Romance: Western Vulgar Latin: Asturian aceptar, Portuguese aceitar, Catalan acceptar, French accepter, Italian accettare
acerca (Preposition) "near"

12th cent. From the Latin phrase ad circa of the same meaning. See a for an etymology of ad; see cerca for an etymology of circa.

Romance: Western Vulgar Latin: Portuguese acerca
acercar (Verb) "to approach"

12th cent. A verb created from acerca.

Romance: Western Vulgar Latin: Portuguese acercar
-acho Noun-forming suffix, often with a pejorative sense. m

Perhaps from Latin -atio, a noun-forming suffix used to indicate the end result of a verb. From -at-, a supine verb ending, and -io, a suffix used to form abstract nouns from verbs (see -ío).
acordar (Verb) "to agree," "to decide;" (reflexive) "to remember"

13th cent. From Vulgar Latin *accordare, from a(d)- "toward" (see a-), cor "heart" (see corazon), and verb-forming suffix -are.

Romance: Western Vulgar Latin: Asturian acordar "to remember" but also "to choose," Portuguese acordar, French accorder, Italian accordare "to grant," "to tune (an instrument)," "to agree"

Celtic: Goidelic: Old Irish creitid "to believe;" Brythonic: Middle Welsh credu 'id.,' Middle Breton crediff, Cornish cresy

Indo-Iranian: Indo-Aryan: Sanskrit śrad-dhā- "to believe"

The variety of meanings among the Romance languages, even in Spanish's closest relatives, shows that the Latin term was semantically broad.
acorde (Adjective, Noun) "according;" "musical chord"

An adjectival form the 15th cent. From acordar.

Romance: Western Vulgar Latin: Asturian (Central Asturias) acorde, Portuguese acorde, Galician acorde, Catalan acord, Old French acorde
acto m. (Noun) "act"

13th cent. A learned form of Latin actus 'id.' The native word is auto (2). From agere "to do," "to drive." See -igar.
actuar (Verb) "to act;" "to activate"

16th cent. borrowing from Medieval Latin actuare 'id.,' a verb formed from Latin actus "act" (see auto (2), as well as acto).