The International Standard Bible Encyclopedia

Let

(katecho): Usually in the sense of "permit" (Anglo-Saxon, leetan), but also in Old English with meaning of "hinder" (Anglo-Saxon, lettan). This latter sense is found in 2Th 2:7 the King James Version, "Only he who now letteth will let," where the Revised Version (British and American) has, "Only there is one that restraineth now."

The International Standard Bible Encyclopedia, James Orr (1915). Public domain, from the CrossWire SWORD module.