The -escu ending
The hallmark of Romanian surnames is -escu, a patronymic meaning “descendant of” or “son of.” Popescu is “son of the priest,” Ionescu “son of Ion (John),” Florescu “descendant of Florea.” It’s the Romanian cousin of the Italian -esco.
Trades, land and peoples
Others come from occupations (Popa, “priest”; Ciobanu, “shepherd”; Diaconu, “deacon”), from the land (Munteanu, “highlander”; Moldovan, “from Moldavia”) or from neighbouring peoples (Rusu, “the Russian”). Romanian is a Romance language, so many roots are Latin, with a Slavic layer on top.