E. गिर् speech, in the mominative case, गीः and पति master, Visarga becomes स and स is here changed irregularly to ष the compound however is sometimes written differently, thus गीःपति, गीर्पति or गीस्पति.
ROOTS:
गिर् गीः पति स स ष गीःपति गीर्पति गीस्पति