Where does “дописывать” come from?

дописывать (Russian) comes from Russian дописа́ть, from Russian писа́ть, from German pissen, from Middle Low German pissen, from Dutch pissen, from Middle Dutch pissen, from Old French pissier, from Vulgar Latin pissiare — I piss.

дописывать (Russian): to finish; to write; to write in addition, to add

Definitions

to finish; to write; to write in addition, to add

Ancestry of “дописывать”, step by step

Step	Language	Word	Meaning
1	Russian	дописа́ть	to finish (writing)
2	Russian	писа́ть	to write
3	German	pissen	to piss; to piss down
4	Middle Low German	pissen	—
5	Dutch	pissen	to piss
6	Middle Dutch	pissen	to piss
7	Old French	pissier	to piss; to excrete urine
8	Vulgar Latin	pissiare	present active infinitive of *pīssiō
9	Latin	pissio	I piss

Every word from Latin pissio →Every word from Vulgar Latin pissiare →Every word from Old French pissier →