elanya

'Boob' in English first occurs as an insulting term for a person in 1909; the OED has a quote from the Saturday Evening Post, 03/27: "I had to tell her the boob had gone for the day." as the first instance. This was derived from the noun 'booby', which had been used for several centuries as a noun for a simpleton or dunderhead. The first instance of 'booby' in this sense in English was 'Patient Grissil 48 [Welshman loq.]' (I have no idea what that is) from 1599-1603: 'Then, mage a pooby fool of Sir Owen. God's plude, shall!' This sense of 'booby' is probably derived from Spanish bobo, which was used very early to mean 'fool', although there is also a Middle High German 'buobe' which also means 'fool', which is considered less likely.

The term 'boob' or 'booby' used to refer to the breast is much later, being of American slang origin, and originally in print in Henry Miller's 1934 Tropic of Cancer (as 'booby'), and in Miller's 1949 Sexus (as 'boob'), according to the OED, though no doubt used verbally before that time. These were not derived from the Spanish 'bobo', but from the 17th century term 'bubby', which derives from the dialectal German Bubbi (teat).