-z

An eye dialect spelling variant of -s.

From a mutation (specifically a zetacism) of the rhotic consonant /ɹ/ to /z/.

While standalone suffixation (such as soz and Baz) gained wide recognition in British print during the 1980s, the underlying morphophonological shift is attested significantly earlier in Australian English via the derived non‐rhotic suffix -zza (such as Bazza for Barry), which has been in print since at least the 1960s.