Willful

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Middle English: from the noun will2 + -ful.

etymonline

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willful (adj.)

also wilful, c. 1200, "strong-willed," usually in a bad sense, "obstinate, unreasonable," from will (n.) + -ful. From late 14c. as "eager" (to do something). Mid-14c., of actions, "done on purpose, intentional, due to one's own will." Related: Willfullness.