A purpose to serve.

1

1815.  When I see a merchant over-polite to his customers, thinks I, that man has an axe to grind.—C. Miner, ‘Who’ll turn Grindstones?’ (N.E.D.)

2

1842.  He has an axe of his own to grind, just like the rest of us.—Mrs. Kirkland, ‘Forest Life,’ ii. 68.

3

1854.  Delazon is some on flattery, especially when he has an ax to grind.—Weekly Oregonian, Dec. 9.

4

1862.  

        Long ’z A. ’ll turn tu an’ grin’ B. ’s exe, ef B. ’ll help him grin’ hisn,
(An’ thet ’s the main idee by which your leadin’ men hev risen).
Lowell, ‘Biglow Papers,’ 2nd Series, No. 3.    

5

1869.  She laughed at him because he never called unless he had an axe to grind.—E. E. Hale, ‘Ingham Papers,’ p. 121.

6