Sluggish

google

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late Middle English: from the noun slug1 or the verb slug (see sluggard) + -ish1.

wiktionary

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slug +‎  -ish

etymonline

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sluggish (adj.)

mid-15c., from Middle English slugge "lazy person" (see sluggard) + -ish. Earlier adjective was sluggi (early 13c.). Related: Sluggishly; sluggishness.