ETYM Pref. a- + side.
1. In reserve; not for immediate use; SYN. by, away.
2. On or to one side.
3. Out of the way (especially away from one's thoughts); SYN. away.
4. Placed or kept separate and distinct as for a purpose; SYN. apart.
Inclining or directed to one side; Bram Stoker.