Middle English slaken, from late Old English sleacian, slacian "become slack or remiss; relax an effort" (intransitive); "delay, retard" (transitive), from slæc "lax" (see slack (adj.), and compare Middle Dutch, Middle Low German slaken).
The transitive sense of "make slack, loosen" (ropes, a bridle, etc.) is from late 12c. The sense of "allay, diminish in force or intensity, quench, extinguish" is from late 13c. in reference to fire, c. 1300 in reference to thirst, hunger, desire, wrath, lust, etc. The notion is "make slack or inactive." Related: Slaked; slaking.
updated on December 16, 2022