The Yuletide-lads originate from Icelandic folklore.
Early on their number and depictions varied greatly depending on location, with each individual Lad ranging from a mere prankster to a homicidal monster who eats children.
In 1932, the poem "Jólasveinarnir" was published as a part of the popular poetry book Jólin Koma ("Christmas Is Coming") by Icelandic poet Jóhannes úr Kötlum. The poem reintroduced Icelandic society to Icelandic Yuletide folklore and established what is now considered the canonical thirteen Yuletide-lads, their personalities and connection to other folkloric characters.
The Yuletide-lads were originally portrayed as being mischievous, or even criminal, pranksters who would steal from, or otherwise harass the population (at the time mostly rural farmers). They all had descriptive names that conveyed their modus operandi.
The Yuletide-lads are traditionally said to be the sons of the mountain-dwelling trolls Grýla and Leppalúði. They would trek from the mountains to scare Icelandic children who misbehaved before Christmas. Additionally, the Yuletide-lads are often depicted with the Yule Cat, a beast that, according to folklore, eats children who do not receive new clothes for Christmas.
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