refrain; avoid taking or using
The doctor has told me that if I don't begin to abstain from alcohol from now on, I shall be dead within five years.
ab, abs (from, away from)#tenere (to hold) (Latin)
this can be written as "ab+stai. and stai. sounds like stay. and. stay out of something means not involving in sth that doesn't concern to one. ab+stain. we tend to stay away from stain.