early 15c., "in fact, in reality" (as opposed to in possibility), from actual + -ly (2). Meaning "actively, vigorously" is from mid-15c.; that of "at this time, at present" is from 1660s. As an intensive added to a statement and suggesting "as a matter of fact, really, in truth" it is attested from 1762.
1. He actually became convinced that the nurses had an unanswerable case.
2. They actually moved down from upstairs because the rent's that expensive.
3. He will actually be serving three concurrent five-year sentences.
4. I actually knew her, but in overalls I passed unrecognised.
5. "Actually, most of my tennis is at club level," he admitted.