1747 W. Hooson sig. L3 Leap..is when the Vein is thrown of from its perpendicular Course, at once into the Side; these Leaps never happen, but at some Way-board, or large Bed-joynt.
1855 J. R. Leifchild 109 Vertical Intersections.—These are commonly called leaps, or throws.
1874 J. H. Collins (1875) Gloss. 136/2 at Fault. If [the displacement of strata is] upwards, a leap or upthrow; if downwards, a slide or downthrow.