surname, early 13c., probably an agent noun from walk (v.) in the sense "to full cloth." preserves the cloth-fulling sense (walker with this meaning is attested from c. 1300). "Walker" or "Hookey Walker" was a common slang retort of incredulity in early and mid-19c. London, for which "Various problematic explanations have been offered" [Century Dictionary].

"Is it?" said Scrooge. "Go and buy it."

"Walk-ER!" exclaimed the boy.

"No, no," said Scrooge. "I am in earnest" (etc.)

[Dickens, "A Christmas Carol"]

1520s, of a people of what is now souther and southeastern Belgium, also of their language, from French Wallon, literally "foreigner," of Germanic origin (compare Old High German walh "foreigner"). The people are of Gaulish origin and speak a French dialect. The name is a form of the common appellation of Germanic peoples to Romanic-speaking neighbors. See Vlach, also Welsh. As a noun from 1560s; as a language name from 1640s.