Apparently from the same as dowd; the breast (as the seat of love, or from its shape) -- breast, teat.
see HEBREW dowd
H1717. dad
[דַּד] noun masculineProverbs 5:19 breast, better teat, nipple (τιτθοί Aq 5:19 Symm Ezekiel 23:3, 21; Late Hebrew & Aramaic דַּד; primitive caressing word; according to Fl in NHWBi. 489) — Du. construct דַּדֵּי 23:3, 8) both strike out ᵑ6 ᵐ5 Co); suffix דַּדַּיִךְ 23:21 (read ᵑ6 בתוליך Co); דַּדֶּיהָ Proverbs 5:19; — of breasts of woman 5:19; (Hi Bi read דֹּדֶיהָ her love compare 7:18); of Samaria & Jerusalem under figure of young women Ezekiel 23:3 (בְּתוּלֵיהֶן דַּדֵּי) compare 23:8; דַּדַּיִךְ 23:21; but probably strike out ׳ד in Ezekiel compare above & GeiUrachrift 397. — See also שַׁד below שׁדה.
דֹּדָה דֹּד, see below דוד.