'gynandrousness' originates from New Latin (or Modern Latin) and ultimately from Greek: specifically from New Latin 'gynandrus' (from Greek elements), where the prefix/root 'gyn-' (from Greek 'gynē') meant 'female, woman' and 'andr-' (from Greek 'anḗr, andrós') meant 'male, man', plus the English suffix '-ness' forming a noun meaning 'state or quality.'

'gynandrousness' changed from the Greek compound 'gynandros' (gyn- + andros) into New Latin 'gynandrus' and the English adjective 'gynandrous', and the modern English noun was formed by adding the suffix '-ness' to produce 'gynandrousness'.

Initially it meant 'having both female and male parts' (as described by the Greek compound), and over time it has retained that core sense as the English noun meaning 'the state of being gynandrous.'