Green’s Dictionary of Slang

productive of an exclamation of amazement.

1921		Tatler 6 July 10/2: Even in those days poor humanity had its trials the short-skirted fairy with puffy, windgally fetlocks, a gawdelpus kind of hat, teeth like the keys of a piano, and a will of her own.
1930		Tatler 14 may 20/2: His Portrait-of-a-Lady is of the real Gawdelpus brand. A violently blue background howls unto the skies. An amazingly proportioned figure distorts a frock that seems to be made of melted glue.