google
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late 17th century: frequentative of the verb snug.
wiktionary
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First attested in 1687. snug + -le( frequentative suffix); spelt with doubled ‘g’ to clarify pronunciation.
etymonline
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snuggle (v.)
1680s, frequentative form of snug. Related: Snuggled; snuggling. As a noun from 1901.
