Artificial intelligent assistant

thesterly

ˈthesterly, a. and adv.
  Forms: 1 þeosterlic (adj.), 4 þiesterliche (adv.).
  [f. thester a.: see -ly1, -ly2.]
  a. adj. Dark. b. adv. Darkly.

c 1000 ælfric Hom. I. 504 Þæs muntes cnoll mid þeosterlicum ᵹenipum eal oferhangen wæs. 1340 Ayenb. 244 Þe clene of herte þet hier ssole ysy him be byleaue, ac alneway þiesterliche.

Oxford English Dictionary

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