1.
See let slip out.
2.
Also,
slip away or off. Leave quietly and unobtrusively, as in She slipped out without telling a soul, or Let's slip away before the sermon, or Jason and Sheila slipped off to Bermuda. The use of slip with away dates from about 1450;
out from the first half of the 1500s;
off from the mid-1800s.




