From www.m-w.com
3camp
Function:
noun Etymology:origin unknownDate:circa 1909
1: exaggerated effeminate mannerisms exhibited especially by homosexuals2 a: something so outrageously artificial, affected, inappropriate, or out-of-date as to be considered amusing b: a
style or mode of personal or creative expression that is absurdly
exaggerated and often fuses elements of high and popular culture <a movie that celebrates camp>
Most likely not the first meaning above. Hence,
camp as knickers: amusingly excessive in style
CJ