'angiospermousness' originates from Modern/New Latin (from 'Angiospermae' / 'angiosperm'), where the Greek root 'angeion' meant 'vessel' and 'sperma' meant 'seed', combined with the adjectival suffix '-ous' and the nominalizing suffix '-ness'.

'angiospermousness' changed from the scientific/Modern Latin formation 'angiosperm' (Greek 'angeion' + 'sperma') into the adjective 'angiospermous' in English, and finally into the noun 'angiospermousness' by adding the suffix '-ness'.

Initially the root formation emphasized 'vessel-seed' (a contrast with 'naked seed' of gymnosperms); over time 'angiospermousness' has come to denote the general quality or state of being an angiosperm (a flowering plant).