the meaning of "ur"

From the Oxford English Dictionary online:

repr. G. (also MHG., OHG.) ur-, denoting ‘primitive, original, earliest,’ as ur-Hamlet, -origin, -stock, etc. See also URHEIMAT, URSCHLEIM, URSPRACHE, URTEXT.
G. ursprache (= primitive language) has been freq. used in recent English philological works.

[1864 MAX MÜLLER Lect. Sci. Lang. (1871) II. 133 The most troublesome of all vowels, the neutral vowel, sometimes called Urvocal, better Unvocal.] 1889 JACOBS Caxton's Aesop I. 37 Any light he can throw on the Ur-origin of the Fables. 1901 BOAS Kyd's Wks. p. xlv, The Ur-Hamlet may have contained a number of these borrowings. 1926 A. MØLLER tr. Pedersen's Israel I. I. 245 The word shm is found in all Semitic languages and belongs to the absolutely certain ur-semitic components. 1927 A. H. MCNEILE Introd. to Study of New Testament iii. 50 It was an Ur-Evangelium, a primitive written Gospel, some say in Hebrew, some in Aramaic, on which our Gospels were based. 1937 O. JESPERSEN Analytic Syntax 142 Some well-known students of language who even call this [sc. ‘S is P’] the ‘urform’ of sentences. 1943 V. NABOKOV in Atlantic Monthly May 69/2 The dreadful vulgarity, the Ur-Hitlerism of those ludicrous but vicious organisations. 1947 AUDEN Age of Anxiety (1948) ii. 46 For Long-Ago has been Ever-After since Ur-Papa gave The Primal Yawn that expressed all things. 1949 F. FERGUSSON Idea of Theater i. 26 An enactment of the Ur-Myth of the year~god. 1950 Psychiatry XIII. 168/2 The concept of ur-language and ur-symbolism is of particular importance in Freud's thought. 1964 C. S. LEWIS Discarded Image iv. 54 Plato's ur-Freudian doctrine of the dream as the expression of a submerged wish. 1966 Punch 9 Nov. 718/2 Above is Leonardo da Vinci's design for an ur-tank. 1971 Astrophysics & Space Sci. X. 363 (heading) Orientation of galaxies and a magnetic ‘urfield’. 1977 Listener 31 Mar. 416/1 The importance of the folk example which he [sc. Bartók] argued to be one of the ur-sources of music. 1979 Ibid. 14 June 831/1 Sir Nikolaus Pevsner's ur-history, Pioneers of Modern Design. 1983 Sunday Tel. 13 Mar. 14/6 Russell Hoban is an ur-novelist, a maverick voice that is like no other.