The change from polemos to ptolemos is an example of a type of linguistic compounding called terpsimbrotos. The pt- in ptolemos (vs. earlier polemos) "war" is thought to arise from a re-analysis of the compound word *phere-t-polemos, metathesised to phere-ptolemos. George Dunkel, "Two old problems in Greek: πτόλεμος and τερψίμβροτος", Glotta70:3/4:197-225 (1992) JSTOR40266932.