Latin word summa comes from Proto-Indo-European *eḱs, Latin *eks-uper, Proto-Indo-European *uperi, and later Latin superus (Being above.)
*eḱs (Proto-Indo-European)
out of , out, out of
*eks-uper (Latin)
*uperi (Proto-Indo-European)
super (Latin)
Accusative [of measure] above, beyond, over, in addition to. Accusative [of place] above, beyond. Accusative [of place] above, on the top of, upon.
superus (Latin)
Being above.