Old English æftan "from behind, behind, farthest back," superlative of Old English æf, af, of "away, away from, off" (from PIE root *apo- "off, away"). Cognate with Old Frisian eft "later, afterwards; as well," Old Norse eft "after," Middle Dutch echter, efter "later, again," Gothic afta "behind, past." The Germanic superlative suffix *-ta corresponds to PIE *-to (compare Greek prōtos "first," superlative of pro "before"). The word is now purely nautical, "in, near, or toward the stern of a ship."
adverbial suffix expressing direction, Old English -weard "toward," literally "turned toward," sometimes -weardes, with genitive singular ending of neuter adjectives, from Proto-Germanic *werda- (cognates: Old Saxon, Old Frisian -ward, Old Norse -verðr), variant of PIE *werto- "to turn, wind," from root *wer- (2) "to turn, bend." The original notion is of "turned toward."
Old English æfterwearde "behind, in back, in the rear," from æft "after" (see aft) + -weard suffix indicating direction (see -ward); expanded by influence of after. Variant afterwards shows adverbial genitive. Old English also had æfterweardnes "posterity."