Full of foam or bubbles; light and insubstantial or lacking in depth or seriousness.
From 'froth,' which comes from Old Norse 'frotha.' The '-y' suffix makes it an adjective. Originally described the physical foam on waves or drinks, but evolved to metaphorically describe things that are superficial or empty.
Medieval people called the foam on top of beer 'frothy' as a sign of good quality, but today we use it to insult ideas—saying an argument is 'frothy' means it's full of air and has no real substance, which is a clever metaphor!
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