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 2 Thessalonians 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."

From the International Standard Bible Encyclopedia
Edited by James Orr, published in 1939 by Wm. B. Eerdmans Publishing Co.