"in or to a field," 1590s, contraction of Middle English prepositional phrase in felde, from Old English on felda "in the field" (especially of battle); see a- (1) + field (n.). Meaning "away from home, at a distance" is attested by early 15c.
the armies were afield, challenging the enemy's advance
unlawful to carry hunting rifles afield until the season opens
such digressions can lead us too far afield
affrighten
affront
Afghan
Afghanistan
aficionado
afield
afire
aflame
aflaunt
aflicker
afloat