Green’s Dictionary of Slang

shagger n.1

[shag v.1 ]

1. [20C+] one who copulates; a sexual enthusiast.

2. [1970s] a nuisance, a lazy, disobedient person.

3. [1970s] any thing or person.

In compounds

shagger’s back (n.)

[1980s+] (orig. Aus.) a particularly painful backache, supposedly the result of over-enthusiastic copulation.