Actually, "two blocks" goes back at least to the 1500's. It is "...the condition when two blocks of a purchase have come together by
hauling on the fall."

"Sailors Log," Bradley, 1583.

"Thomas Stewart" wrote in message ...
Two Blocked mean tackle drawn up as tight as it will go before breaking.
The term comes from motorized hoisting Equip. It is a very dangerous
condition for big Equip.

For "Dinghy" it means no adjustment left.

OT