Yay, it's time for that friday feeling :D ...finding recs for this was actually harder than I thought it would be, because looking for stories that are purely origin or backstory, not how they first met or how they joined SHIELD turned out to be tricky. SO here are a few that have lots of backstory or origins in them, but probably have other things too. All brilliant writing and I love them!

For Natasha:
RED by Waldorph (explicit, 9807 words, warnings: attempted rape, brainwashing)
fade in on a girl by waketosleep (mature, 2297 words)
you could burn matresses anywhere by yugimutos (weatheredlaw) (teen and up, 811 words)
The Only Soldier Now Is Me by samalander (mature, 13491 words) more comics background, but comics knowledge not required
Chrysalis by sugar_fey (R, 1028 words, warnings: mentions of child abuse, murder and psychological torture)
there are demons dancing through your dreams by callmebombshell (teen, 1185 words)

For Clint:
come and go blues by gyzym
still officially lost by pollyrepeat (teen and up, 11913 words)

Um, I need more Clint origin stories it seems!