Çäðàñòè Äåñè!
Actually,
Desislava does come from
Desislav:
Desislav was as common as
Desislava back around the 11-12th century, although nowadays the male form is almost extinct.
Mike - I just saw that you have
Desislav as "Derived from the Slavic elements desi, possibly meaning "ten", and slav "glory".
The "desi" part is believed to come from the archaic verb "desiti" - to search for. The "deset" (ten) you refer to is not Slavic - it's just a slavinized version of the Latin "decem"