DTX175, This might answer A few of your questions, from the OED
Anglo-Saxon, n. and adj.
a. The English language as spoken before c1150; Old English.
1678 G. Hickes Ravillac Redivivus 77 I confess I have a great veneration for our own and the Northern English language, upon the account of the Anglo-Saxon..to which they are so nearly ally’d.
1698 Philos. Trans. (Royal Soc.) 20 445 The manuscripts..are written in these Languages, viz. Hebrew,..Malayan, Malabaric, Russian.., Anglo-Saxon, English, and one Book..of the Hieroglyphicks of Mexico.
1783 Bailey’s Universal Etymol. Eng. Dict. (ed. 25) Anglosaxon, the Saxon language as it was spoken in England.
1876 H. Sweet Anglo-Saxon Reader xi The oldest stage of English before the Norman Conquest is now called ‘Old English,’ but the older name of ‘Anglo-Saxon’ is still very generally used.
1884 N.E.D. (at cited word) In this Dictionary, the language of England before 1100 is called, as a whole, ‘Old English’… Anglo-Saxon, when used, is restricted to the Saxon as distinguished from the Anglian dialects of Old English.
1955 R. Quirk & C. L. Wrenn Old Eng. Gram. 1 In the eighteenth and nineteenth centuries the term Anglo-Saxon..was the commonest name for the language; but..it has gradually been replaced in the last hundred years by the more scientific term Old English.
2001 A. Frantzen in P. Pulsiano & E. Treharne Compan. Anglo-Saxon Lit. v. xxvi. 478 English literature was a popular topic and Anglo-Saxon was compulsory within it.
b. The English language, esp. considered as plain, forthright, unaffected, or crude. Hence: coarse, profane, or obscene language.
1866 J. C. Gregg Life in Army xv. 137 Occasionally a word of honest, hearty Anglo-Saxon, or a ‘bit of the brogue’, to remind you that you are not in Naples, but in New Orleans.
1872 H. A. Wise Seven Decades Union 141 He [sc. Senator Leigh of Virginia] was a purist in his Anglo-Saxon.
1917 in Amer. Speech (1929) 4 271 I like your stilted style best Jack. When you descend to the Anglo Saxon you get too much in dead earnest.
1927 Yale Rev. Jan. 414 Tell me what you forget and I will tell you what you are, says the psycho-analyst. But I can do this, too, and in plain Anglo-Saxon. The man who insists on telling me what he forgets is a fool.
1947 K. Malone in Word Study Oct. 2/2 In current speech Anglo-Saxon often means plain English. In this use, the word has Latin for antonym.
1999 Richmond (Virginia) Times Dispatch (Nexis) 28 Dec. f2 Pardon my Anglo-Saxon, but it’s been one hell of a year.