It’s called ripple because when you insert the new clip the effect is to move the next clip further right along the timeline to allow the new clip to fit in and this effect then ripples along the timeline as each other clip moves to the right by the same amount.
It ins’t called insert, because ripple does other things. e.g. moving a clip to the right or left with ripple-on also moves all the other clips to the right of that one by the same amount.
The icon to the right of RIPPLE is called RIPPLE ALL TRACKS and when the clips on the track you are working on ripple, so do the clips on the other tracks.
If you hover over the icons a tool-tip will appear saying what the icon is called.
There is a glossary of terminology here: