I think it's just a phrase. It's projection of human nature on situation. You know, in human world woman called "mother" gives birth. In that scene Oram was going to give a birth. So David called him "mother". That's it.
I speculate it's a reference to Mother as in the WY mainframe cpu. David could have been commenting obliquely of a few steps ahead of his aims where 'Mother' is to be the carrier for all his dastardly experiments
That makes the most sense thank you. I always thought it had something to do with the face hugger implanting the egg into the host and the host symbolized the "mother". Which makes a lot of sense. Cool symbolism they through in there
David sees himself as the father and any human host as the mother of an alien, the egg was waiting for a host to respond. An alien host serves the purpose of a mother by being used to give birth to the creature. I would say David sees the mother role as beneath the one of a father, his conclusion through his own experiences with humans; Weyland, Vickers, Shaw.
To him the alien puts any human in a passive and emasculated condition, like the one he was forced to be on, he was pretty much Weyland's housewife, thus the creature presents the perfect revenge he wanted to use against humans.
Could be option 3 if a third prequel was to have Daniels suffering a similiar fate to Shaw. Maybe serving as the raw material for David's first queen.
But if you only look at the two movies we got, option 1 seems to be the most likely, as Oram was impregnated and delivered David's "baby" and the eggs stayed inert until their host or mother arrived.