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").
Old French accident