If I remember correctly in one of the descriptions for Samurai, it said humans saw it and copied him.
For Viking. Many cultures around the world made axe like weapons and covers themselves up in cold environments. He was also challenged by many warriors, so he was well known.
Every predator that sticks around will get a name for itself and possibly people will mimic them in some capacity, definitely so for impressionable cultures.
That’s how myths and legends are born. Someone sees something, they tell people rumors spread, and are expanded upon until the original is unrecognizable