Where does “sillyly” come from?

sillyly (English) comes from English silly, from Middle English seely, from Old English sǣliġ, from Proto-West Germanic sālīg, from Proto-West Germanic -g, from Proto-Germanic -gaz, from Proto-Indo-European -ḱos — -y, -ic.

Ancestry of “sillyly”, step by step

sillyly traces back through two separate lines of ancestry.

via English silly

StepLanguageWordMeaning
1EnglishsillyLaughable or amusing through foolishness or a...
2Middle Englishseelyhappy
3Old Englishsǣliġblessed, fortunate; happy, prosperous, blessed
4Proto-West Germanicsālīgblissful, prosperous, happy
5Proto-West Germanic-gForms adjectives from nouns and verbs with a...
6Proto-Germanic-gaz-y
7Proto-Indo-European-ḱos-y, -ic

via English ly

StepLanguageWordMeaning
1EnglishlyAbbreviation of light-year
2VietnameselyAlternative spelling of li
Every word from Proto-Indo-European -ḱos