The Collaborative International Dictionary of English v.0.48:

Haply \Hap"ly\ (h[a^]p"l[y^]), adv.
   By hap, chance, luck, or accident; perhaps; it may be.
   [1913 Webster]

         Lest haply ye be found even to fight against God.
                                                  --Acts v. 39.
   [1913 Webster]

WordNet (r) 3.0 (2006):

haply
    adv 1: by accident; "betrayed by a word haply overheard" [syn:
           haply, by chance, by luck]