ECS - Exported fields origin of rsa.foo.*

I'm currently implementing 'ECS' for our in house products and I was wondering what the origin or meaning of the 'rsa' fields are?
It is unusual in that they span multiple vendors and am wondering what the 'rsa' acronym stands for.

Examples:
rsa.internal.msg_id from cisco fields and juniper fields

What does the 'rsa' acronym stand for?

It comes from GitHub - blookot/rsa2elk: Converts Netwitness log parser configuration to Logstash configuration and was used as an easy way to create some of the modules. It will go away in the future as the Agent integrations are built out.