What does this phrase mean -
"Load of old tosh" ?

In various places on this site, I see the expression 'load of tosh', 'complete tosh', etc. to describe something as useless - but I can't find anything on the website about where this word came from! What IS the origin of 'tosh'?

Even the Oxford English Dictionary doesn't claim to know. It was first sighted in 1892, already meaning "nonsense, rubbish, twaddle", just as it does now.