Origins of a Superstition

In light of GroundHog's Day I was reading an article from the Today Show on 13 superstitions that are still persistent today, and their origins. It was all pretty common place until I came upon this one...
Umbrella opened indoors

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Why is it so wrong to open an umbrella indoors?
Because you don't want to offend the spirit of the umbrella, silly!
Consider these insights from Richard Webster's reference work "The Encyclopedia of Superstitions":
"A common superstition is the belief that opening an umbrella inside a house causes bad luck. The origin of this is that the umbrella acts as a shield against the sun or rain outdoors. To open it indoors offends the spirit of the umbrella, who will cause bad luck to occur as a result."

I had never thought about why you're not supposed to open the umbrella indoors, and now knowing the reason, it makes me laugh, because that is as mythological as you can get! Trying not to offend the spirit of the umbrella, because all things have a spirit.