Attachments :
From the OED.  It does not give an etymology, however:
Obs. rare.


    Enchantment, sorcery.
  a1225 [see SIGALDER n.]. 13.. K. Alis. 7015 (W.), Quede and harme he wil me spye,..Gef he wot of this sygaldrye [Laud trigoldrye] That this trowes [= trees] kan lye. ?a1500 Chester Pl., Crucifixion (Shaks. Soc.) II. 69 Burye hym wher thy wil be, But look thou make no sigaldry To raise him up agayne.


Obs. rare.

    A charm or incantation.
  c1000 Saxon Leechd. I. 388 Sy{asg}e-{asg}ealdor ic begale, si{asg}e ~{asg}yrd ic me we{asg}e . a1225 Ancr. R. 208 Sigaldren [v.r. sigaldrie], & false teolunges, leuunge on ore & of swefnes, & alle wichchecreftes.

    Hence {dag}sigalder v., to enchant, bewitch. Obs.
  1303 R. BRUNNE Handl. Synne 503 {Th}ere was a wycche, and made a bagge, A bely of le{th}yr ,..She sygaldryd so {th}ys bagge bely {Th}at hyt {ygh}ede and soke mennys ky.