What does 'onding on snaw' mean?

Question

It was a very grey day; a most opaque sky, “onding on snaw,” canopied all; thence flakes felt it intervals, which settled on the hard path and on the hoary lea without melting. (Jane Eyre)

‘Onding' has the meaning ‘the act of continued outpouring or falling; a continuing torrent, as of rain. (dictionary.com). Then, it seems very similar to the Chinese phrase “雪上加霜”(frost on snow) that means ‘what is worse or to make matters worse.’ Is it a possible match? If yes, what else expressions are possible with the meaning?

Answer 1

To begin with, the correct quotation is

It was a very grey day; a most opaque sky, “onding on snaw,” canopied all; thence flakes fell at intervals, which settled on the hard path and on the hoary lea without melting. [emphasis added]

Perhaps you got your text from the Cliff’s Notes, which appear to contain errors.

The use of quotation marks by the author is the clue: the author is letting you know that the phrase “onding on snaw” is not ordinary English, but something unusual, perhaps a dialect peculiar to the place where the story is set. One source gives the meaning as “on the verge of snowing”, but other examples seem to indicate that onding can also have the meaning given at Dictionary.com, Scottish dialect for “the act of continued outpouring or falling; a continuing torrent”:

By this time an onding o’ rain was coming up’ frae the water, and I bade the man come indoors to the fire. (The Moon Endureth—Tales and Fancies by John Buchan)

I was at Tilliedrum yestreen, meeting Sanders as he got out o’ the gaol, and that awfu onding began when we was on the Bellies Braes. We focht our way through it, but not a soul did we meet; and wha would gang out the day that can bide at hame? (The Little Minister by J.M. Barrie)

“It’s going to snow—” she said, as she stood beside him, surprised by the sound of her own voice amid the roar of the wind. ¶ “Aye—it’s onding o’ snaw—” said the shepherd, his shrewd blue eyes travelling over her face and form. “An’ it’ll mappen be a rough night.” (The Case of Richard Meynell by Mrs. Humphry Ward)

Answer 2

From what I can tell, onding from the Scottish means a continuous fall of rain or snow and it is usually specified by adding an o' snaw (snow) or o' rain. where the o', of course, means of.

From Charles Keith’s The Farmer’s Ha’ (1774) “Rain we’ll hae, Or on-ding o’ some kind at least”

It's a little curious that 'on snaw' is used in your quote, but nevertheless I think the meaning here is clear: "a fall of snow"

Answer 3

"a forceful continuous beating down (of snow or rain), or the threat thereof" This is the most comprehensive, precise, and accurate definition I can give through my analysis as a linguist, on the basis of gathering up what other knowledgeable ones have said in bits and pieces. If this definition is substituted in place of "onding" in the literature involving Scottish dialect, it works very well.