'moiety' originates from Old French 'moiete' (also spelled 'moitié'), ultimately from Latin 'medietas', where 'medius' meant 'middle'.

'moiety' changed from Old French 'moiete/ moitié' into Middle English 'moite' and eventually became the modern English word 'moiety'.

Initially, it meant 'half' (from Latin 'medietas'), but over time it expanded to mean 'a portion/share' and acquired a technical anthropological sense of 'one of two social divisions'.