I sympathize with your comment. It's the 'little Swedish words' that give me the most frustration. I have tried to find a reference that provides a comprehensive explanation of the circumstances in which one uses i, på, till, etc. but have been unsuccessful so far. I guess this means we must learn by our errors and when someone says 'that's just the way we do it in Swedish' I have to put on my zen hat and move on rather than venting my frustration and risking getting downvotes. Good luck, John.
The word actually did use a soft k originally, or at least its origins did, as it comes from killing (meaning "kid" as in "goat offspring"). It likely changed to a hard k since it's onomatopoetic. Other common words that went through this are e.g. kissa, as bynny2015 mentioned above, and kisse (meaning "cat") - from the sound one might make to call on a cat: kss kss kss!
Going a bit further off topic, ran across tös in a bob hund song. Seems to translate as girl until you put an adjective or article in front when it becomes rather unflattering. Guess it should be avoided but was wondering if anyone knows the etymology. Wiktionary doesnt have much to say on it.