As in living under the bridge? Or some other context?
Paradox daughters had trolls with gems in their belly buttons, as I recall.
At the time he was first given the name, he was in his late 60's, had a bald head and long grey beard, and always dressed in black.
One day my mom and he were visiting a relative of my mom's. The relative's husband came in, greeted my mom by name, then said to my dad, 'And how's the old troll today?"
The name "Old Troll," and then, "Troll" stuck. Mostly because my dad liked the name and started asking everyone to call him that.
When he moved to Moncton, New Brunswick, he would introduce himself to people as "Troll," and ask them to call him that.
Soon enough, staff of any store or restaurant he'd walk into would greet him with a happy, 'Hello Troll!'