Green’s Dictionary of Slang

tankie n.

[they are ‘built like a tank’]

(UK juv.) a very fat person.

OnLine Dict. of Playground Sl. 🌐 tankie adj. derog. derogatory name used to describe an obese person.
[US]Philadelphia Dly News (PA) 24 July A7/2: ‘Tankie’ as they called the husky teen.