Square-Set or Peasant Sleeve
From the Pattern Description: This beautiful sleeve style has been unjustly neglected by many designers, perhaps because it is not as familiar as other styles. Certainly it cannot be overlooked because of any inherent technical difficulty, because it is one of the easiest of all to knit. It involves practically no shaping whatever. Both the top of the sleeve and the adjoining side of the garment are perfectly straight lines, without increases, decreases, or short rows. This simplicity of line lends itself to a multitude of different pattern treatments and delightful touches of decoration.
Location of Pattern: Basic Design No. 10 - page 97 from Knitting from the Top.