This word is a bit tricky, because SIS can only be used as a verb. In this SIS yoD it looks like it is a noun-noun-construction, but it probably a shortened or archaic form of something involving a verb.
Cite this entry
Definition of {SIS yoD}
from the Klingon Language Wiki:
https://klingon.wiki/Word/SISYoD
Retrieved 27 Mar 2023