The paper deals with an oddity in Latin morphology: the fact that a number of nouns (margō, ōrdō, cardō, homō and nēmō), in spite of being masculine, have, contrary to the general tendency, the G. S. in -inis instead of -ōnis. Some of the nouns (margō, ōrdō, cardō), unlike the other masculine nouns, retained their original G. S. form in -inis (which traces back to Old Latin *-ones) presumably due to analogy with the large group of feminine nouns in -dō, -gō because they have the same consonant at the end of stem. The G. S. of another exception, homō, is explained by analogy with the neuter nouns of the type nomen, nominis. The author also argues that the majority of G. S.-ōnis of feminina abstracta in -iō (type nātiō, -ōnis) can be explained phonologically without referring to their gender. Refs 8.