Green’s Dictionary of Slang

dash v.1

[from the dash that replaces the ‘am’ in dash, i.e. d—n, and subseq. in other ‘obscenities’; note Captain Alexander Smith, History of the Lives of the Most Noted Highwaymen (5th edn, 1719): ‘If we have here and there brought in some of these wicked offenders venting a profane oath or curse, which is dashed, it is to paint them in their proper colours’]

1. [late 18C+] a general euph. for damn v., used in excls. and oaths.

2. as past participle of sense 1; usu. as I’m dashed if... or I’ll be dashed...

In exclamations

dash it (all)!

[19C+] a general euph. excl.

dash my buttons! (also dash my old crabshells, ...sconce!! ...timbers!, durn my buttons!)

[late 18C–1910s] a mild oath.

dash my rags!

[mid-19C-1920s] a mild oath.

dash my wig(s)! (also dash my jasy! dish my wig!)

[late 18C–19C] a mild oath.