dot: [OE] The underlying meaning of dot seems to be ‘small lump or raised mark’. In Old English (in which there is only a single record of its use) it meant ‘head of a boil’, and it could well be related to English tit ‘nipple’. The word disappears from written texts between the 11th and the 16th centuries, and resurfaces in the sense ‘small lump’. The modern meaning ‘small roundish mark’ does not appear until the 17th century. Dottle ‘unburnt tobacco in the bottom of a pipe’ [15] is a diminutive form of dot. => dottle, tit[dot etymology, dot origin, 英语词源]