Affectionate kisses, or to kiss someone in an affectionate way.
From Dutch 'smooch' or possibly imitative in origin, meant to represent the sound of kissing. It entered English slang in the early 20th century as informal, playful language.
Smooch became wildly popular American slang during the Jazz Age (1920s), when young people were being scandalously affectionate in public—the word itself sounds like what it means, which is why imitative words often feel modern and fun.
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