Virtually blind, but not wholly so, what the French call ber-lue; our parblind. (Old English suffix sam, half; or Old High German sand, virtually.) It is only fit for a Launcelot Gobbo to derive it from sand, a sort of earth.
“This is my true-begotten father, who, being more than sand-blind,
high-gravel blind, knows me not.” —
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894