Green’s Dictionary of Slang

tach n.

[backsl.]

a hat.

[UK]Hotten Dict. of Modern Sl. etc.
[UK]A. Stephens ‘The Chickaleary Cove’ 🎵 And a doesn’t care a flatch, / So long as I’ve a tach, / Some pannum for my Chest – and a tog on!
[UK]Sl. Dict.