Etymology: < Anglo-Norman and Middle French obscur, oscur (French obscur ) without light (c1130 in Old French), difficult to understand (c1165), dark in colour (c1165), little-known (1559), of lowly birth (1611 in Cotgrave) and its etymon classical Latin obscūrus dark, dim, hidden from sight, not clear to the mind, incomprehensible, uncertain, imperceptible, dark or dingy in colour, undistinguished, insignificant, humble, perhaps < ob- ob- prefix + a suffixed form of the Indo-European base of sky n.¹ Compare Spanish oscuro (1184; 1490 as obscuro), Italian oscuro (a1292), Portuguese obscuro (16th cent.). With use as noun compare Old French oscur, Middle French obscur darkness (second half of the 12th cent.), that which is unintelligible (1549), dark part of a picture (1690), and classical Latin obscūrum a dark or obscure place or thing, also obscūra people of humble origin, uses as noun of neuter singular and plural respectively of obscūrus.In sense A. 3b after post-classical Latin obscurus in the same sense:1568 T. Smith De Recta et Emendata Linguæ Anglic. f. 14 Si Galli suum habent fœmininum obscurum, siue fuscum e, quod in fine dictionis positum, propè nihil sonat, auditur tamen, & apud illos est frequentissimum, nostræ linguæ prorsus incognitum.1653 J. Wallis Gram. Linguæ Anglicanæ i. 6 Eodem loci..formatur Gallorum e fœmininum; sono nempe obscuro.1653 J. Wallis Gram. Linguæ Anglicanæ i. 7 Ibidem etiam... Sonatur ò, vel ũ, obscurum.

Etymology: Probably partly < obscure adj., partly < Middle French obscurer to become dark, to make dark (also obscurir, obscurcir; 12th cent. in Old French as oscurer, also oscurcir; French obscurcir), and partly < its etymon classical Latin obscūrāre to obscure, darken, to overshadow, dim, to conceal, hide, to make unclear or unintelligible, to render insignificant < obscūrus obscure adj. Compare Italian oscurare to darken (a1292).