groomzling
When one thought leads to another which leads to another, eventually resulting in an outburst of laughter that is unrelated to anything going on outside the person's head.
J suddenly laughs out loud.
J's friends ask him why he is laughing.
J says, "Oh, it was just a groomzling."
J's friends ask him why he is laughing.
J says, "Oh, it was just a groomzling."