Meaning

verb move (a baby) up and down in one's arms or on one's knees

verb pet

originCompare Scots dandill (“to dander; go about idly; move uncertainly; trifle”), English dialectal dander (“to wander about; talk incoherently; rave”), Middle Dutch dantinnen (“to trifle”) (from French dandiner (“to swing; waddle”)), German dändeln, tändeln (“to trifle, dandle”), Middle Dutch and Provincial German danten (“to do foolish things; trifle”), German Tand (“trifle, prattle”).

Etymology from Wiktionary, CC BY-SA 3.0