The single L spelling is at least late-Latin / medieval in origin, if not older - note the masculine
Calixtus / Calistus. The original Greek feminine name is
Callisto,
Callista is a Latin feminine derivative a masculine (probably family) name, derived from the Greek superlative κάλλιστος kállistos (most good/beautiful/noble). The root is κᾱλός (kālós), the substantive derivative form κᾰ́λλος (kállos) is probably a back-formation from the superlative. The reduction of the geminated (twinned) lambda to a single letter is possibly due to a re-analysis of related names as compounds of κᾱλός (kālós) "beautiful/good" rather than dithematic names in which two independent meanings are paired, e.g. Κᾰλλῐκλῆς (Kalliklês) "beauty/nobility + fame"; however the reduction of Callistus/Callista and
Callisto to Calistus/Calista and
Calisto can also be blamed on a limited understanding of classical Greek grammar by the Latin-speakers using these names — there is an apparent understanding that these names are derived from Greek Kalos, without an understanding that the lambda/l would be geminated (the gemination may not be have been any more apparent in spoken Latin than it is in English).
This message was edited 1/24/2020, 5:29 PM