From -ó + -nk (personal-pronoun suffix). The vowel -ó is explained as an impact of kettőnk (“the two of us”), from kettő (“two”) + -nk (“of us”, personal-pronoun suffix) where the ő is part of the base word but by analogy it began to be used with other numerals and pronouns, along with its harmonic variant of -ó.
-ónk
| Inflection (stem in -a-, back harmony) | ||
|---|---|---|
| singular | plural | |
| nominative | -ónk | — |
| accusative | -ónkat | — |
| dative | -ónknak | — |
| instrumental | -ónkkal | — |
| causal-final | -ónkért | — |
| translative | -ónkká | — |
| terminative | -ónkig | — |
| essive-formal | -ónkként | — |
| essive-modal | -ónkul | — |
| inessive | -ónkban | — |
| superessive | -ónkon | — |
| adessive | -ónknál | — |
| illative | -ónkba | — |
| sublative | -ónkra | — |
| allative | -ónkhoz | — |
| elative | -ónkból | — |
| delative | -ónkról | — |
| ablative | -ónktól | — |
| non-attributive possessive - singular |
-ónké | — |
| non-attributive possessive - plural |
-ónkéi | — |