Tho, pron. pl.
Those. [Obs.] This knowen tho that be to wives bound. Chaucer.
3 other Webster entries under this spelling
Tho (tho), def. art.
The. [Obs.] Spenser.
Tho, adv.
Then. [Obs.] Spenser. To do obsequies as was tho the guise. Chaucer.
Tho, conj.
Though. [Reformed spelling.]
Shades of meaning
Fernald has no entry of its own for tho; he lists it under but.
Where he writes about it:
Tho and altho make as little as possible of the concession, dropping it, as it were, incidentally; as, "tho we are guilty, thou art good;" to say "we are guilty, but thou art good," would make the concession of guilt more emphatic. — from notwithstanding