druffine

Need help
with a translation/meaning of lyrics by The Smiths...
Actually it's not by the Smiths, they're quoting Shakespeare or soooo(???). Me=dumb. Yeah, I need the author of the lines too, if anybody knows them?

Song is Cemetry Gates by The Smiths:

You say, "Ere thrice the sun hath done salutation to the dawn"
And you claim these words as your own
But I've read well and I've heard them said
A hundred times, maybe less, maybe more

If you must write prose or poems
The words you use should be your own
Don't plagiarise or take "on loan"

There's always someone, somewhere, with a big nose, who knows
And who trips you up and laughs when you fall
Who'll trip you up and laugh when you fall

You say, "Ere long done do does did"
Words which could only be your own
And then produce the text from whence was ripped
Some dizzy whore, 1804

I need to know what the bold lines mean.

Thanks in advance to anybody who takes time to answer.

Hugs and yeah, I am fine but completely stressed/busy by work.
Move went okay but I don't have www at home, maybe next week, then things will get better. I hope. *grin*
HUUUUUGS