accustomed

the word 'accustomed' entered english in the late 15th century as the past participle of the now-obsolete verb 'accustom,' which meant to make something a custom or habit. this verb itself was borrowed from the old french 'acostumer,' a combination of the prefix 'a-' (from latin 'ad-', meaning 'to') and 'costume' (meaning custom or habit). the old french 'costume' traces back to latin 'consuetudo,' meaning 'habit, usage, practice,' which is derived from 'consuescere' ('to accustom'), itself formed from 'com-' (intensive) and 'suescere' ('to become used to'). the semantic core has remained remarkably stable, evolving from the literal idea of becoming familiar through repeated practice to describing a state of being familiar or habitual.

the word is a simplex form derived from a past participle. it cannot be meaningfully segmented into productive morphemes in modern english without altering the spelling or obscuring its origin. the core element 'custom' is embedded within it.