Giggle

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early 16th century: imitative.

wiktionary

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Unknown. 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”).

etymonline

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giggle (v.)

c. 1500, probably imitative. Related: Giggled; giggling; giggly. As a noun from 1570s.