Is there a reason to butter the nose of someone having a birthday?

In a few parts of Newfoundland, the southwest coast and the west coast in particular, the traditional birthday trick is what is often known as 'grease face.' The same custom is known in parts of the Maritime provinces of Canada as 'buttered noses.' As early as is convenient on the birthday someone tries to reach from behind the birthday boy or girl and dab on their nose a fingerful of grease, often butter. This is accompanied by best wishes for the year, now lubricated with the greasy face. Among schoolchildren this custom sometimes takes the form of pushing a sweet, creamy cake in the face.

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https://www.heritage.nf.ca/articles/society/newfoundland-labrador-customs.php
Another source said this was done so the birthday person would have a 'shiny day.'