froth

Concise Oxford English Dictionary © 2008 Oxford University Press:
froth/frɒθ/

▶noun

• 1 a mass of small bubbles in liquid caused by agitation, fermentation, or salivating.

  ■ impure matter that rises to the surface of liquid.

• 2 worthless or insubstantial talk, ideas, or activities.

▶verb form, produce, or contain froth.

– derivatives
frothily adverb,
frothy adjective (frothier, frothiest).

– origin ME: from ON frotha, frauth.