ETYMOLOGY
from back (n.) or (adv.) + friend;
possibly originally a friend who ‘kept back,’ and did not come forward to assist, and so was no real friend
EXAMPLE (for n. 1.)
“… And as for my lorde chamberleyn, he is nott yit comen to town. When he comythe, than schall I woote whatt to doo. Syr John off Parre is yowre freende and myn, and I gaffe hym a fayre armyng sworde wyth-in thys iij dayes. I harde somwhatt by hym off a bakk freende off yowrys; ye schall knowe moore here-afftre. …”
From: Paston Letters and Papers of the Fifteenth Century
By Paston family, 1472
Published for the Early English Text Society – Edited by Norman Davis, Richard Beadle, and Colin Richmond. 2004
Lexicophilia 