Green’s Dictionary of Slang

rot! excl.1

[abbr. God rot!]

[late 16C–19C] a general excl. of irritation, disbelief, dismissal; usu. as rot it! rot ’em! rot on!

In exclamations

rot you!

[late 17C; mid-19C–1900s] a general excl. of derision, dismissal, synon. with ‘to hell with you!’.