Green’s Dictionary of Slang

chockablock adj.

[naut. jargon chockablock, ‘said of a tackle with the two blocks run close together so that they touch each other – the limit of hoisting’ (OED); transferred to people this became naut. sl. and thence sl.]

1. [mid-19C+] (also choc-a-bloc, chock-heaping, chuck-a-block) crammed full, crammed together; also as adv.; thus chockablock full.

2. [1970s+] (Aus.) in fig. use, having sexual intercourse.

In phrases

go chockablock (with) (v.)

[1970s] (Aus.) to have sexual intercourse (with.