From the Oxford English Dictionary:
piet, n. and adj.
Forms: ME–16 piot, 16 pyet, 19– pyat , 19– pyot ; Eng. regional (north. and midl.) 17– pyat, 18– piat, 18– piet, 18– piot, 18– pyatt, 18–pyet, 18– pyot; also Welsh English (Pembrokeshire) 18– pyatt, 19– piat, 19– pyat, 19– pyet; Sc. pre-17 poyatt, pre-17 poyit, pre-17 pyit, pre-17 pyote, pre-17 pyott, pre-17 17–18 piot, pre-17 17– pyat, pre-17 17– pyet, pre-17 17– pyot, pre-17 18 piet, 17 peyet, 17–18 piat, 18peat, 18 peiot; also Irish English (north.) 18– pyot, 19– piet, 19– pyet.
Etymology: < pie n.1 + -ot suffix; in many later forms showing remodelling of the ending after -et suffix1. Compare Old French, Middle French, French piot (second half of the 13th cent.), Middle French, French piat (c1393), both in sense ‘young of the magpie’.
The literal meaning at sense A. 2 is likely to be the original sense in English. Earlier currency of the word in Older Scots in this sense is perhaps implied by the surname or nickname Willelmo Pyote (1381).
Now Brit. regional and Irish English (north.).
1. A talkative or impertinent person; a gossip. Now rare.See also tale-piet n. at tale n. Compounds 2.
?a1289 Ancrene Riwle (Cleo.: scribe D) (1972) 71 Me seið up on ancre þet [e]uch an mest haueð an old quene to feden hire earen, þet maðeleð alle þe tale þe me telleð ilonde, An kikelot [glossed] piot.
1574 in J. H. Burton Reg. Privy Council Scotl. (1878) 1st Ser. II. 372 Archie Crosar callit the Pyott.
1774 Dumfries Weekly Mag. 21 June, A perfect pyat!—clink for clink!—Where has the villain learn'd to think?
1814 T. Chalmers Let. in W. Hanna Mem. T. Chalmers (1851) I. 340 From the great officers of State at St. James's,‥down to the little female piets who were taught to squall what they did not understand, ‘No fanatics!’
1855 F. K. Robinson Gloss. Yorks. Words (at cited word), ‘A pawky young pyet’, a saucy young person.
1920 D. Mackenzie Pride o' Raploch 30 The pyots ca'ed her ‘Raploch's quean’.
1996 C. I. Macafee Conc. Ulster Dict. 265/2 Pyot,‥a chatterbox.
a1525 (1448) R. Holland Bk. Howlat (Asloan) 176 in F. J. Amours Sc. Allit. Poems (1897) 53 Thar was Pyotis and Partrikis and Pluwaris.
1568 (1513) W. Dunbar Poems (1998) 225 The pyat‥Feynȝeis to sing the nychtingalis note.
a1600 A. Montgomerie Sonn. v, The pratling pyet matchis with the Musis.
1663 in C. S. Romanes Sel. Rec. Regality of Melrose (1915) II. 61 The said John Scot had climed ane pyet nest in his yaird and spoyled his trees.
1707 in A. W. C. Hallen Acct. Bk. Sir J. Foulis (1894) 470 To david and Ja. ȝets for takeing doun the pyot nest‥2s. 0d.
1745 Scots Mag. June 275/1 The scrieching pyets daubed a' our barn.
1819 Scott Ivanhoe III. ii. 61 Here cometh the worthy prelate, as pert as a pyet.
1829 A. Cunningham Magic Bridle in Anniversary 138 Words specked and spotted like a pyat.
1900 J. G. Campbell Superstitions Highlands vi. 227 Magpie. The pyet‥is called ‘the messenger of the Campbells’.
1965 Jrnl. Lancs. Dial. Soc. Jan. 7 Magpie.‥ Piet, Pyot.
1996 Herald (Glasgow) (Nexis) 12 Oct. 8 The whaup and the mavis, the peesie and the pyat are woven into the plaid of our heritage.
b. The oystercatcher, Haematopus ostralegus. More fully sea piet. Cf. pianet n. 3, sea-pie n.1 Nowrare.
1710 R. Sibbald Hist. Fife & Kinross ii. iii. 46 Hæmatopus Bellonii, the Sea-Piot.
1880 W. Black White Wings xx, There is no screaming sea-pyot to give warning.
1885 C. Swainson Provinc. Names Brit. Birds 188 Oyster catcher.‥ From its deep black and pure white plumage, resembling that of the magpie, are derived the names Pienet. Sea pie.‥ Sea piet.
1996 C. I. Macafee Conc. Ulster Dict. 265/2 Pyot, Piet, Pyet, a bird: (a) the magpie Pica pica; (b) the oystercatcher Haematopus ostralegus.
c. The dipper, Cinclus cinclus. Also water piet. Now rare.
1804 T. Bewick Hist. Brit. Birds II. 16 (heading) Water Ouzel. Water Crow, Dipper, or Water Piot.
1839 W. Jardine Brit. Birds II. 67 The common Water Crow, or Pyet, as it is familiarly termed in Scotland.
1885 C. Swainson Provinc. Names Brit. Birds 30 Dipper (Cinclus aquaticus).‥ The white breast and blackish upper plumage have caused it to be called Piet.‥ Water piet (Scotland).
1999 Western Morning News (Plymouth) (Nexis) 11 May 26 Local names for the dipper include Piet, River Pie, Benny Ducker, Water Colly, [etc.].
B. adj. Chiefly Sc. Now rare.
1. Resembling a magpie in appearance; pied, piebald.In quot. c1638: wearing black and white clothes.
1508 in J. B. Paul Accts. Treasurer Scotl. (1902) IV. 114 Ane pyot hors giffin to the King.
1594 in C. Innes Black Bk. Taymouth (1855) 299 Ane brown pyat meir.
c1638 in J. Maidment Bk. Sc. Pasquils (1868) 56 Pyet preachers with shoulder ruffes.
1723 Caledonian Mercury 7 Nov., A little Pyot White and Brown Shelty.
1772 'H. Clinker' Folly Witless Women 4 They ware a rugh lang hair like a pyet horse.
c1843 T. Carlyle Hist. Sketches (1898) 256 Thirteen score of volunteer guards-royal‥all in‥beautiful pyet plumage.
1887 Trans. Banffshire Field Club 67 When assailed with the usual formula—‘Man on the piet horse fat's guid for the kinkhost?’ he used to snappishly reply ‘butter an' bear caff’.
1924 Swatches o' Hamespun 81 A peer pyot mixter, they're far fae pic black.
2. Chattering, talkative, gossipy; (of words or speech) glib.
1573 in J. Cranstoun Satirical Poems Reformation (1891) I. xlii. 82 Quhen ȝe ȝourselfis ar daft and ȝoung, And hes nocht but ane Pyat toung.
a1578 R. Lindsay Hist. & Cron. Scotl. (1899) I. 225 Werielie brother ȝe haue fyne poyit wordis I wald nocht haue trowit that ȝe had sic wordis.
1578 J. Rolland Seuin Seages (1932) Prol. 89 Her pyat toung, hir poet toung I suld say, Micht suffice weill to preiche in barne or byre.
1820 Scott Monastery II. ii. 52 ‘Brave words—very brave words—very exceeding pyet words,’ answered the Miller.
1862 R. Sim Legends of Strathisla 73 He‥made a fair speech‥and sae he gat him freed, wha was sae weel content that, in his ain blunt way, he said, ‘Verily, brither, ye hae fine pyet words.’
1913 J. Service Memorables Robert Cummell 115 And then quo' she, wi pyet partle