'monoecy' originates from New Latin (or late Latin) and ultimately from Greek, specifically the word 'monoikos' (μονoικός), where 'monos' meant 'one' and 'oikos' meant 'house'.

'monoikos' (Greek) passed into Late Latin/New Latin as 'monoecia'/'monoecius' and then into English as 'monoecy' (and the adjective 'monoecious').

Initially, it carried the literal sense of 'one house' (both sexes in one house); over time it came to be used technically in botany to denote plants bearing both male and female unisexual flowers on the same individual.