/ ˈdɒti; NAmE ˈdɑːti/ adjective ( dot·tier , dot·ti·est ) ( old-fashioned , BrE , informal )
1.
slightly crazy or silly
SYN eccentric
2.
dotty about sb/sth having romantic feelings for sb; being enthusiastic about sth
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WORD ORIGIN
late 19th cent.: perhaps from obsolete dote simpleton, fool , apparently from Dutch dote folly.