The middle piece of a wheel. The word occurs in 1649 (see N.E.D.), but appears first as a dictionary word in Webster, 1828.

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1821.  Lost, a plated Hoop, from my Chaise Hob.—Advt., Mass. Spy, Oct. 24.

2

1858.  

        The hubs of logs from the “Settler’s ellum,”—
Last of its timber,—they could n’t sell ’em.
*        *        *        *        *
And the back-crossbar as strong as the fore,
And spring and axle and hub encore.
O. W. Holmes, ‘The One-Hoss Shay.’    

3