'non-allantois-bearing' is a compound formed from the negative prefix 'non-' (from Latin 'non', meaning 'not'), 'allantois' (from New/Modern Latin, ultimately from Greek 'allant-'/'allantoeis', meaning 'sausage-shaped' and referring to shape), and the English participial adjective-forming element '-bearing' (from Old English 'beran', meaning 'to carry').

'non-' entered English from Latin as a productive negative prefix in Middle English; 'allantois' was adopted into scientific English from New/Modern Latin (itself derived from Greek allantoeis referring to a sausage-like shape) and became established in embryological terminology; '-bearing' developed from Old English 'beran' and the verb 'bear' into a modern adjectival construction (e.g., 'egg-bearing'). These elements combined in modern scientific English to create the compound 'non-allantois-bearing.'

Originally a transparent descriptive compound meaning simply 'not carrying an allantois'; its meaning has remained technical and specific to embryology, denoting absence of the allantois during development.