Please explain translation of 'Dzog-pa-chen-po' or 'Dzogchen'.

Hi all! I have a few thoughts about how I would expect 'Dzog-pa-chen-po' to be translated, which is not the standard way. I'll number my thoughts and give my expected translation. By the way, I have no training at all in Tibetan grammar so I am moreso asking for clarification than to change anyone's minds.

1. dzog: complete, the end, perfection; chen: great, big? (just 'great' is a little vague for me)

2. -pa: indicates doership (ex. 'rig-pa': lit. 'see-er')

3. -po: indicates masculine noun

4. dzog-pa: completer, perfecter, ender; chen-po: greatness

5. dzogpachenpo: the Perfecting Greatness, or maybe 'the Greatness that is the Completer', or the 'Concluding Greatness'

So why is it translated "the Great Perfection" and not "the Perfecting Greatness"? Thanks for your help. May all being realize what they really are.