Description:

The work 'kaca' is an Old Common word that mostly aligns with the English word 'bean', a large seed grown in a pod and eaten for food, and has the same phylogenetic unspecificity.

In Old Common, it narrowly referred to food, and in its rarely-used verbal sense, it was an intransitive pali verb meaning to be a bean. For unclear reasons, though, arising over the middle period and becoming normal in the standard language by early modern period, kaca has taken on some slang meanings that have completely overshadowed whatever its normal meanings would be in a verbal context or derived as a modifier.

Noun:

As a noun, 'kaca' still solidly refers to beans as food. Less stereotypically 'beany' plant products like cocao beans and coffee beans are included in the semantic range, as in English.

Verb:

In a verbal context, the modern meaning is as a transitive skurun verb meaning 'to attack with small projectiles'. The projectiles could be handfuls of pebbles, a stone in a sling, a pellet from an air rifle, or actual beans. This usage comes across as slangy and informal but is increasingly normalised and has completely overshadowed the original sense as a pali verb meaning to be a bean or bean-like, which would sound stilted or stodgy to modern ears. The origin of this sense of 'kaca' is unknown.

If you wanted to specify the type of object thrown, you would use a prepositional phrase with the null preposition.

Modifier:

The modifier form 'kacas' could have a sense of 'bean like' but using it this way would be at least amusing if not confusing to speakers due to being overshadowed by another slangy usage of unknown origin. In the modern language, 'kacas' is a colloquial and slightly cutesy or humouristic way to say that someone is cranky or has an angry disposition, or is likely to respond to interactions negatively or combatively. It's possible that this meaning connects to the verbal sense of pelting with small objects,