šālaš שָׁלַשׁ ‘to do three’ (Hebrew)

Etymology^?: a primitive root perhaps originally to intensify, i.e. treble

šālaš v
1) to do a third time, do three times, divide in three parts
 1a) (Piel) to do a third time, divide into three parts
 1b) (Pual) to be three years of age, be threefold