From the Dictionary of Newfoundland English:
janny n, usu pl also janney, jenny, johnny [phonetics unavailable]. Cp OED johnny 1 'a fellow, chap'; EDD john 2 (6 a) 'the mummers used to be called John Jacks' (1875-) W; O Sup2 janney Nfld (1896-).
1 Elaborately costumed person who participates in various group activities at Christmas; FOOL, MUMMER n.
1896 J A Folklore ix, 36 Old teaks and jannies, boys and men who turn out in various disguises and carry on various pranks during the Christmas holidays, which last from 25th December to Old Christmas day, 6th January. [c1900] 1978 RLS 8, p. 27 ~ a mummer. 1925 Dial Notes v, 335 Johnnies—Christmas mummers. Also jennies. 1928 Nfld Qtly Dec, p. 15 The merry party of 'Jannies,' or 'Mummers' made the welkin ring with their weird shouts and cries and their 'false faces' sent many [a] frightened child in haste to its mother's knee. 1937 DEVINE 29 ~ ies. Mummers; persons dressed in disguise at Christmas for visiting. 1957 Atlantic Advocate xlviii, 23 ... extra large kitchens that served as the stage for the 'Fools' or 'Mummers' or 'Janneys,' to give them their peculiar local names. T 45-64 You had no rhyme or nothing goin' out in these janneys. We usen't. Only get in [a house] and try and talk way they wouldn't understand you or get out and waltz or dance. T 172/3-65 Same thing, janney. Since that, we're not known as mummers today, they're janneys today. T 181-65 They have those johnnies, they calls 'em now. So many boys and girls around, but they got no recitations, see, nothing to say. 1969 Christmas Mumming in Nfld 65-6 There are 'big janneys,' adults, and 'little janneys,' children... Some are able to 'talk like a janney'—ingressive utterances at a high pitch. 1973 PINSENT 55 Apparently this janny had been making the rounds for years and not once had anyone guessed him—till this night. 1973 WIDDOWSON 424 'Now they big Janneys is comin' in! They'll take you tonight if yous don't be good!'
2 Phr go out in the jannies: to dress in the disguise and costume of a Christmas mummer; cp FOOL 2. T 45-64 Oh yes, we went out in the janneys several times down home before we left. 3 Comb janny-night: any night during Christmas season on which jannies go around visiting at people's houses. C 67-2 On janny-night they used to get dressed up and go from house to house. Would dance and get something to eat. Usually had a harmonica or a jews harp... Would go out most nights from Christmas Eve to New Year.
janny-talk: distorted or ingressive speech of a mummer used as a means of disguising one's identity. 1969 Christmas Mumming in Nfld 211 When the janneys come to a house they wish to visit, they open, without knocking, the storm-door, stick their heads inside the 'porch' and 'sing out': 'Any janneys in tonight?' in the high-pitched, squeaky voice that janneys always use—'janney-talk.' T 257-66 Oh yes, 'twas queer talk—janney talk. Some people can't talk and some of 'em can, you know. Some of them make a queer talk, draw in their voice, and make a queer sound.
A primer for listening to Merrybegot by Mary Dalton, read by Anita Best, from Rattling Books.