I am a great collector of lexical derivation methods. I ran across one a while ago — I wish I could remember where — which I immediately grabbed for Kahtsaai (PDF). This resulted in a minor lexical upheaval, but I'm very fond of the results.
The form is -rwa after vowels, -irwa after all consonants except r, l and ł, in which case it's just -wa. For now, it is only attached to verbs. It produces stative verbs meaning that something has the characteristic of causing or permitting the verbal action. That's a bit obscure. Some examples make it clearer:
|łeit fear, be afraid of||łeitirwa scary|
|weir be sick||weirwa contagious|
|posé trust, believe||póserwa trustworthy, believable|
|tááít go to someone for help; seek sanctuary||tááítirwa messed up or dangerous beyond one's ability to cope with alone|
Some of the resulting words are similar to English nouns in -able, but most are not. It seems very useful, and is so far doing a good job of taxing my ability to come up with English definitions for things. What, for example, would this derivation of kén urge, impel, set in motion mean? What about kitra tame, subdue? The notions seem useful.
1 Given as a "Gowachin aphorism" in Frank Herbert's novel Whipping Star.