Feminine rhymes are indeed rarer than in Middle English poetry in consequence of the disuse of flexional endings.
It will fare not otherwise, as I am bold to predict, with the flexional genitive, formed in s or es (see p. 161).
Many of the classificatory and some of the flexional suffixes of Indo-European speech can be shown to have had this origin.
In the Greek dative-locative πόδ-εσ-σι, for example, the suffix -ες is classificatory; in the nominative πόδ-ες it is flexional.
In this phrase, probably owing to confusion with we ynk(en), the verb often has no flexional ending; cp.
flexion flex·ion (flěk'shən)
The act of bending a joint or limb in the body by the action of flexors.
The condition of being flexed or bent.