According to the Dictionary, a lord is "a monarch, ruler, governor, [Milton] Master, supreme person [Shakespeare]; a tyrant, an oppressive ruler, [Hayward]; a husband, [Pope] One who is at the head of any business, an overseer [Turner]; a nobleman [Shakespeare]; a general name for a peer of England [King Charles]; a baron; an honorary title applied to officers, as lord chief justice, lord mayor, lord chief baron; a ludicrous title given by the vulgar to a hump-backed person, traced, however, to the Greek crooked (439). Johnson, not a lord, is a man who calls himself a humble scholar. He uses his posture supposed humility ironically before Chesterfield, as he does the term patron: "When I had once addressed your Lordship in public, I had exhausted all the art of pleasing which a retired and uncourtly scholar can possess. I had done all that I could; and no man is well pleased to have his all neglected, be it ever so little." Johnson thus contrasts his humility as a scholar with that of a lord -- but a lord defined as a tyrant, overseer, even head of a business or ironically titled hump-back, suggesting the power of a lord to be both cruel or kind, and he can use his position for great or nefarious purposes. The ability to use the term ironically to someone ugly or poor seems reversed the letter -- the great but humbly born and poor writer Johnson calls Chesterfield 'lord,' even while he savages the lord's two-faced nature and highlights his own scholarly determination to bring his writing project to fruition. A scholar, in contrast, is less ambiguously defined in the Dictionary as "one who learns to be a master, a disciple [Hooker]; a man of letters [Wilkins]; a pedant, a man of books [Hooker]; One who has a lettered education [Shakespeare]; One who in our English universities belongs to the foundation of a college and who has a portion of its revenues [Warton]" (640). Johnson openly calls himself a scholar and proudly wears the title, even though he conceals (or highlights) his status by stressing his humility. Like his ironic thanks for Lord Chesterfield's support in print once the Dictionary was published and lauded,...

He asserts his dignity time and time again, even though he is a man "struggling for life," whose supposed patron looks upon him with "unconcern" and does not "Encumber him with help." Johnson says he made his achievement in a solitary fashion, thus he has no obligation to than Chesterfield, and also does not desire the lord to imply a patronage relationship in print which never existed between the two of them. Chesterfield's favorable articles in the World aside, Johnson is "unwilling that the public should consider me as owing that to a patron, which providence has enabled me to do for myself. Having carried on my work thus far with so little obligation to any favourer of learning, I shall not be disappointed though I should conclude it, if less be possible." In other words, having survived without patronage, Johnson wants this fact known to the world, and he does not want Chesterfield to take credit for giving support to Johnson, support that never really existed.
Works Cited

Johnson, Samuel. "Letter to Lord Chesterfield." Edited by John Boswell. Complete text available 17 Sept 2008. http://www.ourcivilisation.com/smartboard/shop/johnsons/patron.htm

Johnson, Samuel, George Matthews, Henry John Todd, Alexander Chalmers, & R. Marchbank.

Dictionary of the English Language: In which the Words are Deduced from Their Originals, Explained in Their Different Meanings, and Authorized by the Names of the Writers in Whose Works They are Found. C. & J. Rivington, 1824. Digitized Sep 7, 2006

Google Books. Complete text available. 17 Sept 2008. http://books.google.com/books?id=lqsRAAAAIAAJ&printsec=frontcover&dq=Johnson+Samuel+Dictionary&lr=#PPA528,M1