To move a baby or small child gently and playfully up and down, especially on your knee; to pet or fondle.
From Middle English dandel, possibly from a Scandinavian source (compare Swedish 'dilla' meaning to soothe). The word has meant 'to bounce playfully' since at least the 1500s, and originally may have been imitative of the bouncing motion itself.
Dandle is a surprisingly old word that captures something very specific: that gentle, rhythmic bouncing parents do instinctively. It's one of those English words that describes a feeling—cozy, safe, playful—in a single sound that almost imitates the motion itself.
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