Green’s Dictionary of Slang

(Aus. / US) a small creature, usu. human.

1904		G.V. Hobart Jim Hickey 18: Amy Bishop’s kid is an awful hit with me [...] that li'l tacker understands every word I say to him.
1980		M. Bail Homesickness (1999) 63: And what’s this little tacker’s name?
2000		S. Maloney Big Ask 5: Last time I saw the little tacker he couldn’t have been more than five or six.
2015		N. Cummins Tales of the Honey Badger [ebook] [of a guinea pig] The little tacker carefully walked up to the hollow of the island’s solitary tree.
2021		P. Papathanasiou Stoning 133: ‘As a little tacker, I remember watching planes’.