Can anyone tell me what "d" and "t" mean in this 1921 vintage baby afghan in wheel stitch? The pattern does not give any explanation for the stitches and the person I purchased it from does not know either.

Pattern:
Begin with a chain containing a multiple of 8 and 2 over.

1st row_ Make 8 t in the 5th ch, pulling the loop out long. * Skip 3 chs, 1 d
in next, skip 3 ch, 8 t in next st. Repeat from * to the end of row ending with
a d. Fasten off, turn.