Dad's double (4)

I believe the answer is:
papa
This could be a double definition.
'dad's' is the first definition.
(synonyms)
'double' is the second definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps there's an association between them I don't understand?
Can you help me to learn more?
(Other definitions for papa that I've seen before include "Mama's other half?" , "Daddy]" , "Dad" , "The old man" , "Comms code for 'P'" .)
