In Finnish mythology and lore, menninkäinen are gnomes that are said to live deep in the forests.
In modern usage, the word is usually used to mean goblins, hobgoblins and gnomes. Not all Finnish words for the little folk have an English equivalent, and vice versa, so confusion in the translation of these terms is quite common.
Fairy tale depictions often involve riddling, dominance struggles and favors elicited.
Menninkäinens were probably originally thought to be spirits of dead people, but folklore about them has changed during time, and they turned to be something else.