Unknown. Probably from multiple sources; the sense "treasure" could ultimately be via rhotacism from Proto-Germanic *azaniz (“harvest”), *azniz, while the sense "giant" could ultimately be from Proto-Norse .
aarni (archaic)
| Inflection of aarni (Kotus type 5/risti, no gradation) | |||
|---|---|---|---|
| nominative | aarni | aarnit | |
| genitive | aarnin | aarnien | |
| partitive | aarnia | aarneja | |
| illative | aarniin | aarneihin | |
| singular | plural | ||
| nominative | aarni | aarnit | |
| accusative | nom. | aarni | aarnit |
| gen. | aarnin | ||
| genitive | aarnin | aarnien | |
| partitive | aarnia | aarneja | |
| inessive | aarnissa | aarneissa | |
| elative | aarnista | aarneista | |
| illative | aarniin | aarneihin | |
| adessive | aarnilla | aarneilla | |
| ablative | aarnilta | aarneilta | |
| allative | aarnille | aarneille | |
| essive | aarnina | aarneina | |
| translative | aarniksi | aarneiksi | |
| abessive | aarnitta | aarneitta | |
| instructive | — | aarnein | |
| comitative | See the possessive forms below. | ||