dotty

Concise Oxford English Dictionary © 2008 Oxford University Press:
dotty/ˈdɒti/

▶adjective (dottier, dottiest) informal

• 1 slightly mad or eccentric.

• 2 (dotty about) infatuated with.

– derivatives
dottily adverb,
dottiness noun.

– origin C19: perh. from obs. dote ‘simpleton, fool’.