Murky

wiktionary

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From Middle English mirky; equivalent to murk +‎ -y. Related to Old Norse myrkr, Russian мрак(mrak), Serbo-Croatian мра̑к.

etymonline

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murky (adj.)

"dark, obscure, gloomy," mid-14c., from murk + -y (2). Rare before 17c. The older adjective was simply murk. Related: Murkily; murkiness.