Lawful

wiktionary

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From Middle English laweful, equivalent to law +‎ -ful, conflated with Middle English leful, leeful, leveful(“according to law, lawful, pertaining to law”). See also leveful.

etymonline

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lawful (adj.)

c. 1300, laghful, "rightful, supported by law" (of sanctions, etc.); see law (n.) + -ful. Meaning "allowed by law" is late 14c. Similar construction in Old Norse logfullr. Old English had lahlic. Related: Lawfully; lawfulness.