adjectives - Are the words "sillily", "uglily", "friendlily", "livelily", etc., valid English?

I have wondered about how to make the words silly, ugly, friendly, lively, etc. into adverbs, so I researched in the Internet. I found many different answers, so I tried checking Oxford Dictionaries.

However, Oxford Dictionaries still gave me two answers:

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  this is from Oxford Dictionaries’ online grammar reference, “forming adverbs” page

  
  

  
  

  Adjectives that end in -ly, such as friendly or lively, can’t be made into adverbs by adding -ly. You have to use a different form of words, e.g. ‘in a friendly way’ or ‘in a lively way’ instead

  
  

  
  


• from the dictionary entries: there are results from typing sillily, uglily, friendlily, livelily into Oxford Dictionaries’ website (online dictionary)

That’s quite an obvious contradiction from one of the most famous dictionary providers of the world!

So, are the words sillily, uglily, friendlily, livelily, etc. valid English?

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Note: I already saw the “comparative and superlative adverbs” question that asked about the word sillily but I don't see any sources in there that are trustworthy enough (compared to oxford dictionaries), so I'm asking a new question.

EDIT: I've already reported the mistake to Oxford Dictionaries. They said that those words are valid (although rare) and it's a mistake in the reference, They say they will get it fixed soon.

Answer

If you use the real OED, you will find all these with no trouble:

burlily, chillily, cleanlily, comelily, deadlily, friendlily, ghastlily, ghostlily, godlily, holily, homelily, jellily, jollily, kindlily, livelily, lonelily, lordlily, lovelily, lowlily, manlily, melancholily, oilily, portlily, sicklily, sillily, sprightlily, statelily, surlily, uglily, unfriendlily, ungodlily, unholily, unmanlily, wilily, woollily, worldlily.

So there is clearly ample evidence that this sort of thing exists.

Here in more detail is the OED entry for sillily:

sillily [ˈsɪlɪlɪ], adv.

Etymology: f. silly a. + -ly ².

1. 
   

   Poorly, badly. Obs. rare.

   
   
   
   
   • 1581 Mulcaster Positions xxxv. (1887) 126 — The soule it selfe is but sillyly looked to, while the bodie is in price.
   
   
   • 1611 Cotgr., s.v. Manger, — He that makes himselfe simple shall be sillily vsed.
   
   
   
   


2. 
   

   In a foolish, absurd, or senseless manner.

   
   
   
   
   • 1627 W. Sclater Exp. 2 Thess. (1629) 256 — How doe wee sillily call all Idolatrous, that is in vse amongst Idolaters?
   
   
   • 1658 A. Fox Würtz’ Surg. iii. xi. 248 — Such Wounds which were very deep, and were silily and ignorantly stitched.
   
   
   • 1712 Steele Spect. No. 466 P6 — [She] affects to please so sillily, that..you see the Simpleton from Head to Foot.
   
   
   • 1740–1 Richardson Pamela I. xxiv. 67 — He sat down, and look’d at me, and..as sillily as such a poor Girl as I.
   
   
   • 1805 Spirit Publ. Jrnls. IX. 4 — They sillily interested themselves in the event of a new experiment.
   
   
   • 1843 Mrs. Carlyle Lett. I. 254 — Neither have I sillily paid four or five pounds away for it.
   
   
   • 1864 Browning Dram. Pers. Wks. 1896 I. 573/2, — I took your arm And sillily smiled.
   
   
   
   

So it has clearly been around for a long time.

That should answer your question about whether sillily is “valid English”. Sure, you may not care for it, but it is unquestionably an English word of long-standing use.