A European dialect word for '
Chicken or Hen', but was originally a word/sound used when 'calling chickens (i.e. biddybiddybiddy).
It's quite uncommon to hear it now, but it's an old (mostly
British colloquialism) to refer to old women (of a certain disposition) as 'birds' or 'hens'.
Subsequently, the term 'Biddy' became a term used to refer to an old women, generally
one who is fussy or garrulous.