Green’s Dictionary of Slang

1. silly, foolish; also used affectionately.

2010		Urban Dict. 20 Jan. 🌐 Derpy Awkward or embarrassing, especially pertaining to a person.
2012		C. Eble UNC-CH Campus Sl. 2011 3: DERPY — looking or acting silly: ‘My dog is so derpy.’ Usually endearing.

2. badly made.

2014

C. Eble UNC-CH Campus Sl. Spring 2014 4: DERPY — done ineptly or by mistake: ‘I made cupcakes. Sorry about the derpy one. It fell apart when I tried to ice it’.