Rash
A surname that likely began as a nickname for someone thought rash, bold, or reckless.
The #4,565 most common surname in the United States (2010 Census) — about 1 in every 39,741 Americans shares it.
Etymology
The most likely source is the Middle English word rash, meaning hasty, reckless, or thoughtless. That word was influenced by Old French, and earlier ultimately by Latin; in surname use, it would have functioned as a descriptive nickname. The same root also appears in older surname discussions as a sobriquet-type label for an impetuous person.
History
Bardsley and other early surname writers treated Rash as a nickname surname, and later dictionaries grouped it with other names formed from personal traits. It is a relatively uncommon English surname, with modern bearers in Britain and the United States. Some historical references near this entry also mention Rashleigh, but that is a different surname and should not be confused with Rash.
Origin
Regions
Variant spellings
Fun fact
The modern word rash has long carried the sense of acting too quickly, which makes it a classic source for nickname surnames.
From the historical record
“RASH LEIGH 1 (Eng.) Bel. to Rashleigh, Rash- RASSLEIGH J ley, or Rasleigh (Devon), 16th cent. Rashley= (proh.) Ra's (or the Roe's) Lea [a late genit. of O.E. rd, m., a roe- buck + ledh] RASSELL, an assim. form of Rastall, q.v. RASTALL ) (A.-Fr.-Lat.) the French Rastel, RASTELL I app. a nickname or sign-name from…”
— Surnames of the United Kingdom: a concise etymological dictionary (2 vols in 1)