▁of ▁choosing ▁a ▁new ▁name ▁began ▁in ▁AD ▁ 5 3 3 : ▁Mercur ius ▁de emed ▁it ▁in app ropri ate ▁for ▁a ▁po pe ▁to ▁be ▁named ▁after ▁the ▁pag an ▁Roman ▁god ▁Mercur y , ▁and ▁adopted ▁the ▁name ▁John ▁II ▁in ▁honor ▁of ▁his ▁prede cess or ▁John ▁I , ▁who ▁was ▁v ener ated ▁as ▁a ▁mart yr . ▁In ▁the ▁ 1 0 th ▁century ▁cler ics ▁from ▁beyond ▁the ▁Al ps , ▁especially ▁Germany ▁and ▁France , ▁acc eded ▁to ▁the ▁pap acy ▁and ▁replaced ▁their ▁foreign - s ounding ▁names ▁with ▁more ▁traditional ▁ones . ▁ ▁The ▁last ▁po pe ▁to ▁use ▁his ▁bapt ism al ▁name ▁was ▁Mar cell us ▁II ▁in ▁ 1 5 5 5 , ▁a ▁choice ▁that ▁was ▁even ▁then ▁quite ▁exception al . ▁Names ▁are ▁freely ▁chosen ▁by ▁pop es , ▁and ▁not ▁based ▁on ▁any ▁system . ▁Names ▁of ▁immediate ▁or ▁distant ▁prede cess ors , ▁ment ors , ▁sain ts , ▁or ▁even ▁family ▁members — as ▁was ▁the ▁case ▁with ▁John ▁XX III — have ▁been ▁adopted . ▁ ▁In ▁ 1 9 7 8 ▁Card inal ▁Alb ino ▁Luci ani ▁became ▁the ▁first ▁po pe ▁to ▁take ▁a ▁double ▁name , ▁John ▁Paul ▁I , ▁to ▁honour ▁his ▁two ▁immediate ▁prede cess ors , ▁John ▁XX III ▁and ▁Paul ▁VI ; ▁he ▁had ▁been ▁elev ated ▁to ▁bishop ▁by ▁John ▁XX III , ▁then ▁to ▁Patri arch ▁of ▁Ven ice ▁and ▁the ▁College ▁of ▁Card