'periapsidal' originates from New Latin/Modern English formation, specifically from 'periapsis' + the English adjectival suffix '-al', where 'peri-' (Greek) meant 'around' or 'near' and 'apsis' (Greek) meant 'arch' or 'a point (of an orbit)'.

'periapsidal' changed from the noun 'periapsis' (used in astronomy from New Latin/Modern scientific usage) by adding the English suffix '-al' to form an adjective describing something pertaining to that point, eventually becoming the established technical adjective 'periapsidal'.

Initially it denoted relation to the noun 'periapsis' (the closest orbital point); over time it has remained a technical adjective meaning 'pertaining to or occurring near the periapsis'.