My wife was remarking on our cat Pushkin’s excessive fondness for dairy products when I realized I didn’t know the etymology of the word dairy. Not being one to accept such a state of affairs, I dashed off to consult the OED, and discovered that just as a nunnery is a place where nuns live, a dairy (originally deierie) is (or was) a place where deys work. And what is a dey, you ask? Why, it’s “A woman having charge of a dairy and things pertaining to it; in early use, also, with the more general sense, female servant, maid-servant.” The etymology is as follows:
[OE. dæȝe, corresp. to ON. deigja, maid, female servant, house-keeper (whence Sw. deja dairy-maid):—OTeut. *daigjôn, from ablaut-stem of the vb. (in Gothic) deigan, daig, dig-un, digan-, to knead; whence Goth. daigs, OE. dáȝ, dáh, dough.
The primitive meaning ‘kneader’, ‘maker of bread’, appears in OE. in the first quotation; in ON. and in early ME. we find the wider sense of ‘female servant’, ‘woman employed in a house or farm’. Cf. also ON. bú-deigja (bú, house, household) and mod. Norw. bu-deia, sæter-deia, agtar-deia. The same word, or a cognate derivative of the same root, is understood to form the second element in OE. hlæfdíȝe, hlæfdiȝe now LADY. See also DAIRY.]
So dough is ‘that which is kneaded,’ a dey was originally the woman who kneads it (whence ‘female servant’ and then specifically ‘woman who works in a dairy’), and a lady was a loaf-kneader. Isn’t that interesting?
A few citations for dey (which is apparently still used in the Caithness region of Scotland):
c1386 CHAUCER Nun’s Pr. T. 26 She was as it were a maner deye.
16.. in Maidment Sc. Pasquils (1868) II. 262 An old dey or dairy maid at Douglas Castle.
1721 RAMSAY To Gay xvii, Dance with kiltit dees, O’er mossy plains.
c1820 Lizie Lindsay in Child Ballads VIII. (1892) 524/1 My father he is an old shepherd, My mither she is an old dey.