giggle

Early 16th century, probably of imitative origin.

Or, perhaps a frequentative based on dialectal English gig (“to creak”), from Middle English gigen (“to make a creaking sound”) +‎ -le; or perhaps of Dutch or Low German origin: compare Saterland Frisian güüchelje (“to giggle”), West Frisian giechelje (“to giggle”), Dutch giechelen (“to giggle”), German Low German giecheln (“to giggle”), dialectal German giggln, gigglen (“to giggle”), German gickeln (“to giggle”). All of these words are likely onomatopoeic as well. Also compare Alemannic German Guege (“fiddle”).