Willingly means gladly and by your own free choice. Do it willingly, willingly agreed, went willingly.
It is used most often to make a contrast with force or reluctance, which is why willingly and under duress appear in the same sentences. Not willingly is a firm refusal. Note willing, which as an adjective means ready to help — a willing volunteer; unwillingly; and willingness, which is what employers ask for in references when they cannot praise the work.
1adverbwillinglyGladly and by your own free choice.
“He willingly gave up his seat to the old woman.”
willingly is a manner of consent.
Old English willendlice comes from willan, to want or intend — the same root as will, the noun and the verb. Willingly is doing something from your own will rather than another's.
Old English
willendlīċe — diligently
Middle English
willyngly
English, today
willingly
Built from
From Middle English willyngly, wyllyngly (“intentionally, deliverately; freely, gladly”), from Old English willendlīċe (“diligently”), equivalent to willing + -ly.
Etymology from Wiktionary, CC BY-SA