Troll

Troll: (1) (n) disruptive individual on a website, blog, chatroom who deliberately causes problems, writes insulting or otherwise inappropriate things.
(2)(n) fairy tale creature, dangerous, often found under bridges used by goats, especially of the gruff sort
(3)(v) to fish by running a fishing line behind a moving boat
(4)(v) to seek out companionship from another by moving from location to location at a party or bar
(5)(v) to move about constantly at a social gathering in an attempt to be sure everyone else is having a good time.
Now, boys and girls, for extra  credit, can you tell me how this one word accumulated such dissimilar meanings?
I must admit, the last is totally new to me, courtesy of a client, and has the most disturbing implications (except that one about the terrible creature under the bridge, and then mostly if you're a goat). Why do we get caught up in the trap of thinking that others' happiness is our responsibility? Maybe if we were the host or hostess at some elaborate party, we might have some cause to be concerned that our guests were happy. But this is more about our need to have everything happening the way we want.
Sure, sometimes it has to do with the co-dependents' focus on another's happiness over their own. What we are talking about here, this variation on "trolling," is making sure our expectations are met; in a word: control. 
When people do not show up at our events (regardless of reason/excuse), it becomes a personal rejection. When they do not enjoy/appreciate our efforts to have everything go well, we see it as our own failure. And the typical response is not to look for the causes (which might have nothing to do with us), but simply to double down on our efforts to make sure the same things go better next time!
The possibility that there might be nothing that could be done never occurs to us, is not acceptable to us.
Expectation is a cruel mistress, and we get stuck in a vicious circle: we set (unrealistic) goals, then feel a failure, so we set the bar higher for the next time. Only when we are able to accept what is, rather than what we expected to be, and enjoy the here and now, can we conquer the troll.