Definition of "unsifted"

[…] You speak like a green girl,Unsifted in such perilous circumstance.

c. 1599–1602 (date written), William Shakespeare, “The Tragedie of Hamlet, Prince of Denmarke”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act I, scene iii]

But each man’s understanding, such as it is, must be his guide; and he, who has not courage to make a free use of it, but obtrudes the opinions of others, unsifted and unexamined, on his readers, betrays more want of respect for their understanding, than diffidence of his own.

1765, George Colman, The Comedies of Terence, Translated into Familiar Blank Verse, London: T. Becket & P. A. De Hondt, 2nd edition, 1768, Volume I, Preface, p. xxxii