The lightest touch that means something — a fingertip's knock; on screens, the smallest yes.
Old French taper (to tap, to pat lightly), probably imitative of the sound itself; the lightest touch that still means something has always been named for the small sound it makes, not for any force behind it.
The lightest touch that means something, a fingertip's knock, or on a screen, the smallest yes. Named for the sound of the touch rather than for any weight behind it.