'appendicial' originates from Latin, specifically from the noun 'appendix' (from Medieval Latin 'appendix'), where the verb 'appendere' meant 'to hang upon' or 'attach'. The adjective-forming suffix '-ial' comes from Latin via Old French.

'appendicial' developed from the Late Latin/Medieval Latin noun 'appendix' and the Latin/Old French adjectival suffix '-ial', entering English as a learned adjective meaning 'of or relating to an appendix'.

Initially, the root referred to 'something hung on or attached' (an attached part); over time the derived adjective came to mean specifically 'relating to an appendix' (either a book appendix or the anatomical appendix).