The phrase in question comes from 「カタカナ英語と和製英語：最近の傾向を中心として」からの抜粋. The text describes words in Japanese that appear similar to English words and are written in katakana. I am having trouble understanding this:

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> マイブーム(英語{えいご}で言{い}えば「私{わたし}のにわか景気{けいき}」の意{い}。
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What specifically does 私のにわか景気 mean? It sounds like *My unexpected condition*. But that seems like a strange translation.

Any help?