Severally, adv.
Separately; distinctly; apart from others; individually. There must be an auditor to check and revise each severally by itself. De Quincey.
Shades of meaning
Fernald has no entry of its own for severally; he lists it under apiece.
Where he writes about it:
Individually emphasizes the independence of the individuals; separately and severally still more emphatically hold them apart. — from apiece
The signers of a note may become jointly and severally responsible, that is, each liable for the entire amount, as if he had signed it alone. — from apiece