Present participle of squabble; engaging in petty quarreling or arguing noisily over trivial matters.
Probably imitative of the sound of fighting, similar to Swedish skvabbla 'to splash, babble.' First recorded in the 17th century, originally describing the noisy quarreling of birds, later applied to humans.
Like many words for arguing, 'squabbling' is beautifully onomatopoeic - it sounds exactly like what it describes, that harsh, repetitive noise of petty conflict. We literally named this behavior after the sound it makes.
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