Old English forewearde "toward the front, in front; toward the future; at the beginning;" see fore + -ward. Adjectival sense of "early" is from 1520s; that of "presumptuous" is attested from 1560s. The Old English adjective meant "inclined to the front; early; former."
1590s, "to help push forward," from forward (adv.). Meaning "to send (a letter, etc.) on to another destination" is from 1757; later of e-mail. Related: Forwarded; forwarding.