Incidental
来自Big Physics
early 17th century: originally from medieval Latin incidentalis, from Latin incident- ‘falling upon, happening to’ (from the verb incidere ).
wiktionary
From incident + -al.
etymonline
incidental (adj.)
"casual, occurring casually in connection with something else; of minor importance," 1640s, from Medieval Latin incidentalis, from incidens (see incident (n.)). The earlier adjective in this sense was incident (1520s). Incidentals (n.) "'occasional' expenses, etc.," is attested by 1707. Incidental music "background music," originally in operas, is from 1812.
