Where does the phrase 'smack dab' come from?

In essence, the phrase means "slapped precisely in the center." According to the Oxford English Dictionary, smack-dab showed up in print in 1892: "He hit him smack dab in the mouth" [Dialect Notes I, 232].

The first element, smack, is used as an adverb. It is defined as "with, or as with, a smack; suddenly and violently; slap." It appears in 1782 in Cowper's John Gilpin: "Smack went the whip, round went the wheels."

The second element, dab, means "with a dab or sudden contact." Robert Armin's Nest of Ninnies uses it in this sense in 1608: "He dropt downe..as heauy as if a leaden plummet... had fallen on the earth dab."

A variation is slap-dab: "He was goin' that fas' he run slap-dab agin me afo' he seed me" [1886, Turf, Field & Farm XLII. 174/3].

Slap-bang is close, but it meant immediately rather than centered: "Slap-bang shop: a petty cook's shop where there is no credit given, but what is had must be paid down with the ready slap-bang, i.e. immediately" [1785, Grose's Dictionary of the Vulgar Tongue]. In essence, the phrase means "slapped precisely in the center." According to the Oxford English Dictionary, smack-dab showed up in print in 1892: "He hit him smack dab in the mouth" [Dialect Notes I, 232].

The first element, smack, is used as an adverb. It is defined as "with, or as with, a smack; suddenly and violently; slap." It appears in 1782 in Cowper's John Gilpin: "Smack went the whip, round went the wheels."

The second element, dab, means "with a dab or sudden contact." Robert Armin's Nest of Ninnies uses it in this sense in 1608: "He dropt downe..as heauy as if a leaden plummet... had fallen on the earth dab."

A variation is slap-dab: "He was goin' that fas' he run slap-dab agin me afo' he seed me" [1886, Turf, Field & Farm XLII. 174/3].

Slap-bang is close, but it meant immediately rather than centered: "Slap-bang shop: a petty cook's shop where there is no credit given, but what is had must be paid down with the ready slap-bang, i.e. immediately" [1785, Grose's Dictionary of the Vulgar Tongue].