dotty (adj.)youdaoicibaDictYouDict[dotty 词源字典]
1812, "full of dots," from dot (n.) + -y (2). Meaning "silly" is from c. 1400, in dotypolle "dotty poll" (i.e. "dotty head"), in which case the first element is from dote (v.).[dotty etymology, dotty origin, 英语词源]