What Did DiaryTom Know & When Did He Know It?

[Charlie Moody]

No: HPFGUIDX 73549

In CoS, Riddle makes reference to Harry's 'mud-blood mother';  how does 
he know?  DiaryTom was shut up in a notebook for 50 years - and 
arguably knew nothing about James or Lily, neither of whom would have 
been born during DiaryTom's time @ Hogwarts.

If all his information about Harry comes from Ginny Weasley, how does 
SHE come to cough up that particular chestnut?  And, if Ginny knows, 
how could Harry's best friend & resident expert on the WizardWorld (and 
Ginny's brother) have failed to mention that Harry's mother was 
Muggle-born, ESPECIALLY in light of Harry's ignorance of the term 
'mudblood' earlier in the book?

I'll be going back & re-reading all 5 soon (and I'll be taking notes, 
you may be sure!), but pending that:  is there a canonical source for 
the assertion that Lily is Muggle-born (other than Petunia's spiteful & 
self-serving remarks early in HP+tPS)?  Any basis for believing that 
DiaryTom had access to info about Harry's family beyond Ginny?