Likely a back-formation from *Mättyise-, from mättä- (“hill”) + -y + -in.
Mättyisi
| Declension of Mättyisi (type 5/lehti, no gradation) | ||
|---|---|---|
| singular | plural | |
| nominative | Mättyisi | — |
| genitive | Mättyisen | — |
| partitive | Mättyisiä | — |
| illative | Mättyisee | — |
| inessive | Mättyisees | — |
| elative | Mättyisest | — |
| allative | Mättyiselle | — |
| adessive | Mättyiseel | — |
| ablative | Mättyiselt | — |
| translative | Mättyiseks | — |
| essive | Mättyisennä, Mättyiseen | — |
| exessive1) | Mättyisent | — |
| 1) obsolete *) the accusative corresponds with either the genitive (sg) or nominative (pl) **) the comitative is formed by adding the suffix -ka? or -kä? to the genitive. | ||