PIE base ‘to leap, climb’.
Other derivatives include scan, ascend, from Latin scandere ‘to climb’, scandal, from Greek skandalon ‘a snare, trap, stumbling block’, scalar and echelon, from Latin scālæ ‘steps, staircase, ladder’, and Sanskrit skandati ‘he jumps’.
[Not in Pokorny, but De Vann has *skend-, *sknd- ‘to jump up, ascend’, pp. 543–544.]