I think it is something akin to "little devil"?

I don't believe the swedes awake at the moment, but there is a Swedish World Cup team. you could ask one of them

Peterlund is swedish

It probably has some early mythological meaning, like an imp or elf, sort of thing. That is purely judging by your questionable translation, I have absolutely no knowledge of Swedish

Are you it's Swedish? Where did you see the word?

There's team Sweden you could ask

Ja jag är svensk. Det stämmer :)

My Swedish is a little rusty, but I'm pretty sure that peter is saying he has a friend called Sven with a speech impediment. And knarlhat is an exploding hat.

oops meant to say "are you sure it's Swedish?"

"Knalhat" i don't know much about but "knallhatt" says more to me.

detonator, knallhatt, tändhatt
A device that makes gun powder explode.

I googled it and a link popped up that might help:

http://webdiplomacy.net/forum.php?viewthread=1402995#1402995

:)

It is what my grandmother called me. Knalhat is what I understood her to be saying but my spelling probably way way off.

She would always preface it with "little" in English. So, when she was amused by me she'd laugh and say that I was a little knalhat.

An alternate translation I found is squib which can mean a dreamer or a small child, though both are less common uses of the word.

that makes sense, thanks.

Yes also I found "little child" to be an alternative meaning of "knallhatt".
The double "l" and double "t" after the "a"s means that the "a"s should be pronounced short/fast. Did she?

Thanks all, I was writing a poem in which that memory played a part.

A few swedes and lots of turnips

All above is proberly right but there is one more meaning. Its also in swedish mythology the name of a gnome (think is right word. Swedish
Vätte) that spreads discord and chaos for the farmers (if he been bad to the gnomes). Normaly they help the farmers but if they dont get helped back they get angry, folklore
Is full of exampels where the milk turn sour or the cows die. So a knallhatt is the hitman if the gnomes, evil, cunning and full of mayhem, and sent in to do the job.
This folklore is verry much from the northern part of sweden, she from there?

She was born in 1897. She was from Trollhatten in Vastergotland.

The folklore definition might explain my preference for playing gnomes in Dungeons and Dragons though :-)

My Dad did say the being a "Knallhatt" wasn't really a good thing.