ETYMOLOGY
from slow (adj.) + back (n.)
EXAMPLE
“…For God doth not assiste slouthfull persons and idle slowbackes. Now I call those needelesse occupations, whiche idle and ill disposed people do vse, thereby to be troublesome to their neighbours and to deceiue other men, exercising, I confesse, an occupation, but such an one as is vtterly vnlawfull & vnprofitable to all men…”
From: Fiftie Godlie and Learned Sermons Diuided into Fiue Decades
By Heinrich Bullinger, 1577
Lexicophilia 