Green’s Dictionary of Slang

kye n.1

[ety. unknown; Partridge (1984) suggests the Yid. kye, 18; but this is not cited in Rosen; note kibosh n. (3)]

one shilling and sixpence.

[UK]Sl. Dict. 211: Kye eighteenpence.
[UK]Partridge DSUE (1984) 659: from ca. 1860.