'appertain' originates from Old French, specifically the word 'apertenir', where the prefix 'ad-' (ap-) meant 'to' and the root 'pertinere' (from Latin) meant 'to hold/extend to'

'appertain' changed from Anglo-French/Old French 'apertenir' and Medieval Latin 'appertinere', ultimately becoming the modern English word 'appertain' through Middle English

Initially, it meant 'to reach toward or concern (something)', and over time it kept the basic sense of 'belonging to or relating to' in modern usage