C16: from Latin instillāre to pour in a drop at a time, from stillāre to drip
Word Origin and History for instill
v.
also instil, early 15c., "to introduce (liquid, feelings, etc.) little by little," from Latin instillare "put in by drops, to drop, trickle," from in- "in" (see in- (2)) + stilla "a drop" (see distill). Related: Instilled; instilling.
instill in Medicine
instill in·still (ĭn-stĭl') v.in·stilled, in·still·ing, in·stills To pour in drop by drop.