KNAVISHLY
craftily, cunningly, foxily, knavishly, slyly, trickily, artfully
(adverb) in an artful manner; “he craftily arranged to be there when the decision was announced”; “had ever circumstances conspired so cunningly?”
Source: WordNet® 3.1
Etymology
Adverb
knavishly (comparative more knavishly, superlative most knavishly)
In a knavish manner.
Source: Wiktionary
Knav"ish*ly, adv.
1. In a knavish manner; dishonestly; fraudulently. Holland.
2. Mischievously; waggishly; roguishly. "Knavishly witty." Gayton.
KNAVISH
Knav"ish, a.
1. Like or characteristic of a knave; given to knavery; trickish;
fraudulent; dishonest; villainous; as, a knavish fellow, or a knavish
trick. "Knavish politicians." Macaulay.
2. Mischievous; roguish; waggish.
Cupid is knavish lad, Thus to make poor females mad. Shak.
Source: Webster’s Unabridged Dictionary 1913 Edition