Dogged

google

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Old English docga, of unknown origin.

wiktionary

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From the verb to dog.

From Middle English dogged, doggid, doggyd(“characteristics similar to that of a dog”), equivalent to dog +‎ -ed.

etymonline

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dogged (adj.)

"having the qualities of a dog" (mostly in a negative sense, "mean, surly, contemptible"), c. 1300, from dog (n.). Meaning "persistent, silently obstinate" is from 1779. Hence doggedly (late 14c.), "cruelly, maliciously;" later "with a dog's persistence" (1773). Related: Doggedness.