dab hand /ˈdab ˌhand, ˈdæb ˌhænd 
/ ▸ noun British informal a person who is an expert at a particular activity: Tony is a dab hand at golf.
– ORIGIN early 19th century : from dab, a 17th-century slang term meaning ‘skilled person, expert’, of unknown origin.
EnglishOxford New American Dictionary
