'autoschediastical' originates from Greek, specifically the element 'autos' and the word 'schediastikos', where 'autos' meant 'self' and 'schediastikos' related to 'making a plan/sketch (on the spot)'.

'autoschediastical' was formed in English as a learned compound from Greek roots (via Neo-Latin formations such as 'autoschediasticus'), combining 'autos-' + 'schediast-' + English adjectival suffix '-ical'.

Initially it meant 'made or devised on the spot (by oneself)', and over time it has retained this sense of 'improvised' or 'extemporaneous'.