I should imagine that Mary O'Hara got the song from Alexander Keith's Last Leaves, where three sets from Greig's collection are quoted. In fact she hasn't used Alexander Robb's text at all, but Bell Robertson's (omitting two verses). Miss Robertson had the verse that is puzzling you as

Ye maun winnow it on your loof,
And stack it all in yer right-hand glove.

"Loof" is "palm". O'Hara has made minor alterations to some verses, mostly by introducing extra words to make the rhythm more regular. From my point of view, these are of no more interest than, say, changes made by Britten in his arrangements of traditional songs; except, I suppose, insofar as people may learn songs from "art music" recordings and mistake them for the real thing.

As Mick mentions, verse 1 line 3 isn't "sae loud and shrill" but "baith loud and shrill" (actually Miss Robertson wrote "both", but of course Mary O'Hara is not singing this song in her natural accent, but in a carefully-rehearsed imitation Scottish one). "drt't" and whaet" are presumably typos for "dry 't" and "wheat".

Now, Bell Robertson didn't sing, though she knew the words to a lot of songs. The tune used is Alexander Robb's (a little elaborated), which is also in Last Leaves. I quote it below, with Robb's first verse, from The Greig-Duncan Folk Song Collection, II no 329A p 483.


X:1
T:Laird o' Elfin
S:Alexander Robb, New Deer, Aberdenshire 1908
B:Greig-Duncan Collection II no 329A p 483
Z:Noted by Gavin Greig
N:Aeolian
L:1/8
Q:1/4=100
M:4/4
K:C
E3|E3 E c2 B2|A2 E E D3 z|E4 E4|D2 E G A2
w:The Laird o' El-fin stands on yon hill Ba ba ba lee-lie ba:
c d|e3 e c2 B2|A E3 D2 C D|E3 D C2 D2|E2 A2 A2|]
w:And he blows his trum-pet loud and shrill And the wind blows aye my plaid a-wa.