Digress

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early 16th century: from Latin digress- ‘stepped away’, from the verb digredi, from di- ‘aside’ + gradi ‘to walk’.

wiktionary

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From Latin digressum, past participle of digredi.

etymonline

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digress (v.)

"to turn away in speaking or writing from the direct or appointed course," 1520s, from Latin digressus, past participle of digredi "to go aside, depart, deviate," from dis- "apart, aside" (see dis-) + gradi "to step, go" (from PIE root *ghredh- "to walk, go"). Or perhaps it is a back-formation from digression. Related: Digressed; digressing.