What does the abbreviation 'dna' mean in the head_operations.py

[nanjingabcdefg]

In head_operations.py, there are several opcodes which use the abbreviation 'dna', for example:
set_visitor                    = 1263 # (set_visitor,<entry_no>,<troop_id>,[<dna>]),

What does the strange abbreviation 'dna' mean? I don't think it stands for 'deoxyribonucleic acid'. Though I have searched in the command database, no information is found, so I have to ask it here

 

[Mad Vader]

I think it actually means 'deoxyribonucleic acid', although 'seed' may be more appropriate. It probably determines exact equipment and facecode when you are specifying troops that can have random equipment and faces.
But that could be wrong.

 

[Caba`drin]

MadVader is correct so far as I know.

(Also, this is a perfect example of a question for the stickied Q&A thread.)