It took experts three years to complete the decipherment of this manuscript.

decipherment 是名词，由动词 decipher（破译、解读）加上名词后缀 -ment 构成。decipher 本身由前缀 de-（表示"去除、解开"）和 cipher（密码、暗号）组成，字面意思是"解开密码"。 decipherment 指"破译、解读（密码或难以理解的文字）"的过程或结果。